I’ve got a series of posts on JavaCard development. There is some hardware that is needed if you want to deploy your JavaCard programs to physical hardware. The cards that I’m using are both chip cards and dual-interface cards (meaning that they both have the chip and can communicate over NFC). They also have magnetic strips on the back. If you want to try the same hardware, this is a listing of what I’ve got. Note that the links in the following are affiliate links. If you purchase through these links, I earn a small commission that goes towards supportin gthis site and my activities.
Blank Java Cards
Java 3 Dual Interface Cards
These are the cards on which I’ll be running my programs.
The JR150 cards are dual interface cards. They can interact both through the chip and wirelessly, making them accessible to Android phones. These cards use the smaller 6-contact version of the chip interface and a printable in card printers. The two that I received came with their keys on a sticker enclosed in the device. They key values were the same as what was listed on the Amazon Listing as example keys. I’m reposting here, should you get these cards and the if the same key applies. The cards come with at least 99 KB of storage and supports RSA encryption of up to 4096 bits.
These cards *only* have the chip interface and are suitable for Java Card 2 applications. It has 40 kilobytes of storage and supports RSA encryption up to 2048 bits.
This inexpensive card reader/writer has a wireless-only interface. On Windows, no driver installation is needed. The operating system immediately recognizes it and makes it available to your programs.
This card reader cost a bit more than the wireless-only, but is able to read either type of card. Though it will be listed as two card readers by Windows, only one mode can be active at a time. It will either read a contactless card or a contact card, but not both at the same time. Like the previously mentioned card reader, the drives built into windows already works with this device.
Magnetic Reader/Writers
Text data can be encoded on the magnetic strips on the card. Note that the text data uses an encoding that does not make all ASCII characters available. The encoding for english letters doesn’t distinguish between upper and lower case letters. Card readers tend to return letters in upper case lettering.
Reader/Writer
If you want to also write information to the magnetic strip on the back of the card, you will want a card writer. Though, don’t put anything confidential on the magnetic card. Those contents tend to be stored in plain text and would easily be lifted by someone else.
This magnetic reader has no capability for writing to a strip. To the computer, it appears as a keyboard. Swiping a card through it will result in the computer receiving keystrokes that correlate to the data on the card. You’ll need to parse the data out. I’ve written about the data encoding in another post that you can find here.
Card Skins
I checked out card printers, and even the cheapest among them is too expensive for handling a small volume of cards. So that my cards were not bear white, I decorated them using “card skins.” These are marketed as decorations for payment cards. I did add a few of these to a couple of payment cards too. At this point in time, the only information on the front of a card is a name and the name of a bank. Most of the relevant information is on the back of the card. If you get one, you’ll need to know if you are planning to place the skin on a card with the smaller 6-contact chip or the larger 8-contact. There exists an American Express with a 10-contact chip. I’ve not seen it in person and don’t know it’s size. If you have a 10-contact card, be aware that these skins might not fit. These are the cards that appear in my videos or my posts.
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Various car manufacturer adopted NACS (Tesla charging interface) as their preferred interface for their cars. Those manufacturers have also said that the cars they’ve already sold which use the CCS interface for charging will be able to acquire an adapter for charging at Tesla super chargers when the network opens. Ford vehicles already have access to the Tesla super charging network. GM had stated that they would have access to the Tesla charging network by Spring 2024. At the time that I’m posting this, 2024 June 12, it is only 8 more days until the first day of summer.
There have been concerns about hitting that date, especially since Tela fired the entire supercharger team. But according to InsideEVs, GM said that it was still on schedule to deliver according to its original deadline. With the first day of summer being only a week away, we will see whether they actually hit that mark.
“We plan to stick to the timeline that we previously announced, and that’s kind of all I can say,” Sanaz Marbley, director of global strategic technology communications at GM, told InsideEVs.
As this rollout occurs, some, including myself, have wondered what this will mean for Tesla drivers. Newer Tesla chargers have much longer cables (Version 4 chargers). But many of the chargers already available have much shorter cables. These cables were meant to only power Tesla vehicles, which have their charge port in the back driver’s side tail light (Tesla drivers always back into the space). Many other vehicles have their charge port further away somewhere on the side of the vehicle. From the perspective of a Tesla charger, the port may also be on the wrong side. This results in a driver either needing to double-park for the cable to reach or use the charger on the “wrong side” from where they parked. Either situation results in two chargers now being unavailable to a Tesla driver.
Tesla states that drivers of other EVs may use the charger on the “wrong” side, as this is necessary for charging. But they ask that drivers not park diagnally. Though I can’t use the chargers yet, I drove a Chevrolet EUV Bolt to a local bank of version 3 super chargers and found that I could only reach the cable if I parked diagnally.
Interesting times are ahead at the Tesla charging banks.
I had to park diagnally for the cable to reach my car.
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The concept of transporting the heat produced by an appliance to the outdoors isn’t by any means new. Whether it is the hot air rising out of an oven or the exhaust from the dryer, it’s a concept implemented for generations. Less common in the home environment, however, is the heat from a computer. There are probably people mining cryptocurrency that have already tackled this problem. Though I’m not mining, I found myself faced with it when rendering video or playing a graphically intensive video game. I recently decided to do something about it. On the days I am working from home, it could sometimes become uncomfortably hot in my office though it is cool in the rest of the house. I thought it would be unreasonable to further cool the house just to make it more comfortable in one room; that feels like a waste of energy. Instead, I decided to evacuate the hot air from the computer before it spills out into the room.
I feel like there should be a ready-made solution available somewhere. But my searches turned up next to nothing. I did find an ant-miner adapter made for connecting a 4-inch hose to the antminer. This is a must have for what I’m doing! Four inches is the same diameter as the exhaust hoses used on many residential dryer. The computer in question is near a window. I started off looking for the adapters that are used for portable air conditions. These are usually made to better blend-in with the windows. I wasn’t able to find any that would work for my purposes. I did however find an adapter that was made for venting the air from a drive-through a window. This was perfect! It also used the same 4 inch fitting that the antminer adapter uses. The last major piece I needed was something to help move the air along the hose.
The exhaust fan on a computer is usually blowing air out into an open room. When that same airflow is directed through the dryer hose there may be some back-pressure to overcome. To compensate for this, was I initially was going to for an additional computer fan on the ant-miner adapter. When I tested this out with the 12-volt fan, the air flow was weak. I even tried slightly over-volting the fan to 14 volts to little effect. This was going to be inadequate. I was going to need a stronger solution. With a little more searching I discovered that I could also get 4-inch inline duct fans. This was perfect! There are a variety of duct fans available. For myself, I got a single speed fan. Other options to consider are do you want an inline fan to have a power switch on it, do you want it to be adjustable speed, and what flow rate you want it to have. The flow rate, usually expressed in Cubic Feet per Minute, tells what volume of air it can move over a minute. The higher this number, the more air it moves.
The window adapter with the vent in place.
Before installing anything I fit the pieces together and turned it on. It was working great! when I turned it on I could see the shutters on the exhaust vent open a little. The fan, though audible, didn’t sound much different from the quiet sound of air flowing from an AC unit. For the installation, I had to remove the screen from my Window. The screen was designed to be easily removed and restored.
The exhast vent on the computer with magnets placed around it.
I wanted to be able to quickly attach and disconnect the exhaust vent to my computer. I’ve placed four magnets around the area of the back of the computer that the hot air comes from. I also placed four screws on the antminer adapter. When I line up the adapter with the magnets, it stays in place. There is also weather stripping material that came with the window adapter that I’ve placed on the edges of the ant miner adapter so that it better captures the hot air.
Adapter and hose magnetically atached to the computer.
Drawbacks
Aesthetically, though the adapter was designed to better blend in with the window, it doesn’t completely blend in. Having to remove the screen from my window makes it visually different from my other windows. That’s a drawback. The exhaust duct is warm to the touch. This is expected, since there is warm air flowing through it. But this also means that some of the thermal energy is leaking through it into the room. An insulated duct could prevent this. Not that the current state is awful. Keep in mind previously 100% of the thermal energy was being dumped into the room before. As you might imagine, the window fitting does not block the transfer ot noise to/from the room as well as the double paned glass. If I were in a noisy environment, this could be problematic. I’d like a way to exchange the hot air with the outside without actually pushing air out the window. I’m sure the negative pressure that this solution puts on the room results outside air beign pulled into other areas of the house. An idea solution would perform the heat exchange with the outside without pushing out the air. That would be an air-condition.
Items Purchased or Suggested
Below you will find affiliate links to items that I used or that I would recomend that someone else consider if they decide to implement a similar solution for themselves.
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I was working with hardware that was sequential in coming off a production line. Looking at the hardwares’ serial number, I realized the numbers were mostly sequential, with the exception of the suffix on the serial number. I realized that I was looking at numbers suffixed with a checksum. I tried out a few checksum algorithms to figure out which one fit. This was only being done from curiosity.
One algorithm of special interest was Luhn’s algorithm. This is the algorithm that is used with IMEI, credit card numbers, and Canadian social security numbers. It’s a useful public domain algorithm. I’ve collected a few implementations of it here.
C++
bool pasesLuhnCheck(const string& cardNo)
{
int nDigits = cardNo.length();
int nSum = 0, isSecond = false;
for (int i = nDigits - 1; i >= 0; i--) {
int d = cardNo[i] - '0';
if (isSecond == true)
d = d * 2;
// We add two digits to handle
// cases that make two digits after
// doubling
nSum += d / 10;
nSum += d % 10;
isSecond = !isSecond;
}
return (nSum % 10 == 0);
}
C#
public static bool CheckLuhnParity(string digits)
{
bool isValid = false;
if (!string.IsNullOrEmpty(digits))
{
long sum = 0;
int parity = digits.Length % 2;
for (int i = 0; i < digits.Length; i++)
{
int digit = digits[^(i + 1)] - '0';
sum += (i % 2 == parity) ? Luhn(digit) : digit;
}
isValid = (sum % 10) == 0;
}
return isValid;
}
Kotlin
fun IsValidLuhnString(entry:String): Boolean {
var sum = 0
var isSecond = false
for( i in entry.length-1..0) {
val multiplier = if(isSecond) { 2} else {1}
val digit = entry[i].digitToInt() * multiplier
sum += digit / 10;
sum += digit % 10
isSecond = !isSecond
}
return (sum % 10) == 0
}
You can find a JavaScript/HTML implementation of it at https://j2inet.github.io/apps/luhns. Though this example doesn’t engage in any network communication, while I encourage you to try it out, please don’t use your bank card. Better yet, if you want to examine the code locally, there is also a download link on that page that contains all of the source code.
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Microsoft has made the MS DOS source code available on GitHub. At the time of this writing, the 1.25, 2.0, and 4.0 versions are available. For those that ever ran it, browsing through it shows some interesting attributes. 85% of the source code is x86 assembler and 13.1% is in C. Typically, programs on MS DOS ran in the same memory space (no surprise, since these versions of MS DOS did not support multi-tasking). In modern development the mechanism that a program used for calling an operating system is abstracted away. With a lot of this source code being written in x86 assembler, the communication between a user program and operating system functions is laid bare. Communication and function calls often occurred through dedicated processor interrupts. Though modern processors still use interrupts (especially for hardware events) much of our communication with modern operating systems don’t have to rely on these. Chances are that you don’t have the equipment to write the compiled images to a disk (do you even have a floppy disk?). But I think it is worth looking through if you ever ran it at any point in your life.
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If you try to invoke the Microsoft Storage Emulator (azurite.exe) and you see the following error, the solution is simple.
C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\Extensions\Microsoft\Azure Storage Emulator>azurite.exe
Azurite Blob service is starting at http://127.0.0.1:10000
Exit due to unhandled error: Error: EPERM: operation not permitted, open 'C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\Extensions\Microsoft\Azure Storage Emulator\__azurite_db_blob__.json~'
The solution is simple. You will likely see this error if your current directory is the same as the directory where the EXE is store. You don’t want to run the program that way. It will result in the program attempting to place its temporary files in that folder. The better way is to ensure that the program’s folder is included in your path variable so that you can invoke it from any folder. The full path to the folder will depend on your edition of Visual Studio. I’m using the Community version. If you are running the Professional version, then replace the folder name “Community” with “Professional” below.
UPDATE: The launch is now delayed until 17 May to give time to replace O2 pressure regulation valve.
Boing is going to make a second attempt to launch its Starliner manned spacecraft. The first attempt was scrubbed because of a stuck valve. The next attempt is scheduled for Thursday 8 May at about 10:11 PM. Emphasis on “Attempt” because there is no guarantee that it will happen. The craft is capable of holding up to 7 people. But for this test flight there will only be three people. Barry Willmore, 61, is a NASA astronaut and former U.S. Navy Captain that will be in command. Sunita Williams, 58, is a former Navy server member, will be piloting. The flight plan for the Starliner includes a stay at the International Space Station for a week before returning the astronauts. If this launches, this will be Boeing’s first manned space flight.
This won’t be the first flight of the spacecraft itself. It first launched in 2019, but failed to rendezvous with the Space Station because of a software error. It was successful in a launch in May 2022. Though after that flight Boeing decided to change the type of tape used on the electrical cables to a material that was more fire resistant since then.
Someone had an NFC card for which I needed the data. There are a couple of ways I could have gotten it from him. One way was to ask him to install an app and scan the card. From the app, he could export the data and send it to me. I don’t generally like to ask people to install apps though. The other option was to make a web page and have him use the web page to scan the card. Key factors here is that he was using a Samsung Android phone and he uses Chrome as his primary driver. Chrome on Android has NFC support.
I needed to make the page in a hurry. It’s a single file web page. You can find it at this URL: https://j2inet.github.io/nfcreader/. You can view the source code completely through this link. If you are viewing this article from your computer and want to run the code on your phone, here’s a QR Code to that same URL.
The Interface
The interface is just a bit of HTML decorated with CSS attributes. We don’t need to explore the CSS to understand the interface. There are a couple of buttons for enabling and disabling a scanner, and a checkbox that, when checked, will cause the NFC card’s serial number to also be displayed.
At the time of this writing, NFC support is still considered experimental. mozilla.org reports support for Chrome 89, Opera 63, Samsung Internet 15.0, and WebView 89. I only tested this in Samsung Internet, Samsung Internet Beta, and Chrome. I only experienced this working in Chrome. Tho check whether your browser supports this API, see if the window object defines NDEFReader. If it does not, then the device doesn’t support reading NFC. Note that it is possible for a browser to have software support for NFC while the device has no available NFC hardware. That’s not something that you can test for.
if (! ('NDEFReader' in window)) {
//This device doesn't have NFC capabilities.
document.getElementById('scanButton').disabled = true;
document.getElementById('stopScanButton').disabled = true;
document.getElementById('lastError').innerText = "Sorry, this app only works on devices capable of reading NFC"
}
Before attempting to read the from the NFC card, you’ll need to create an object and set some handlers. You’ll need to create a new NDEFReader object. No parameters are required for its constructor. On the newly created object, add handlers for onreading and onreadingerror.
We will talk about the body of the onreading method shortly.
Initiating the Scan
You can initiate a scan just by calling the scan() method on the NDEFReader object with no parameters. I don’t suggest that though. You will probably want to pass an abort object to the method. This gives you a method to deactivate the scanner at will. For this purpose, I’ve created an AbortController instance.
ar abortController = new AbortController();
The scan method returns a promise. We can use this to know if something went wrong or if the application decided to terminate the scanning. The object returned in this promose is defined by us. On the object I return I may have an isError and reasonText object.
The onreading handler is given an event object. That object has a few elements of concern to us. One is serialNumber, which is a string that contains the serial number for that specific NFC card. The other element is message, which contains a NDEFMessage object. That’s where we will find most of the data! The NDEFMessage object has a field called records; that is a list of the NDEF records written to the card. You may typically encounter NFC cards that only have one message on it, but it can have multiple messages. If you iterate through this object on a non-empty list, you will find one or more NDEFRecordobjects. These are the fields from the record that I find to be the most important.
Field
Explination
recordType
The type of record. It could be the strings "empty", "text", "url", "smart-poster", "absolute-url", "mine", or "unknown". It could also be a custom domain name and custom type separated with a colon(:).
mediaType
Returns the mime type of the record.
data
Returns the raw byte data of the record’s payload.
encoding
The encoding used for a text payload. This could be null.
Iterating and Displaying the Records
For displaying the records, I build a few HTML objects and populate their innerText with the values. I optionally include the serial number to the card. I’m only displaying the record type and the text data. For the card that I needed someone to scan, I knew that this would be sufficient for my purposes. I displayed both the text representation of the data and the raw bytes themselves. Displaying the raw bytes was just a matter of converting the byte values to numeric strings. The browser provides a TextDecoder object for this purpose.
utf8decoder = new TextDecoder('utf8');
...
dataTextElement.innerText = utf8decoder.decode(record.data.buffer);
Here is the complete text for what happens when the card is detected.
reader.onreading = (e) => {
var rootResultElement = document.getElementById("scanResult");
rootResultElement.innerText = "";
var showSerialNumberChecked = document.getElementById('showSerialNumber').checked;
if(showSerialNumberChecked) {
var serialNumberElement = document.createElement('div');
serialNumberElement.class = 'serialNumber';
serialNumberElement.innerText = e.serialNumber;
rootResultElement.appendChild(serialNumberElement) ;
}
for(var i=0;i<e.message.records.length;++i)
{
var record = e.message.records[i];
var envelopeElement = document.createElement('div')
envelopeElement.className = 'ndfmessage';
var typeText = document.createElement('div');
typeText.className = 'recordType'
typeText.innerText = record.recordType;
var dataElement = document.createElement('div');
dataElement.className = 'ndefdata'
dataElement.innerText = bufferToString(record.data.buffer);
var dataTextElement = document.createElement('div');
dataTextElement.innerText = utf8decoder.decode(record.data.buffer);
envelopeElement.appendChild(typeText);
envelopeElement.appendChild(dataElement);
envelopeElement.appendChild(dataTextElement);
rootResultElement.appendChild(envelopeElement);
}
}
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I’ve been exploring Samsung Knox. For enrollment on my test devices, I had initiated a hard reset of the phone and used the secret gesture to get the device in enrollment mode (draw a plus on the initial welcoming screen). While reading through Knox documentation, I encountered a support document with a URL I had not seen before. https://me.samsungknox.com.
As it turns out, by going to this site you can enroll a device without performing a hard reset. This initiates Bluetooth Enrollment. You do need to have a device sitting by with Knox Deploy installed to push the profile to the device.
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I came across something that I thought was cool, though not something I would ever use. It was a set of C++ defines for Japanese language coders that let’s them write in C++ using Japanese words in the place of various C++ control statements and key words. The repository for this project can be found at https://gist.github.com/HerringtonDarkholme/2dbb2a1ec748a786f54908320447b3dd. Here are a few lines from the code.
#define エスティーディー std
#define アイオーストリーム <iostream>
#define ユージング using
#define イフ if
#define インクルード #include
#define イント int
You can probably guess what is going on here, but I will explain. The Japanese characters here are Katakana. They are commonly used to phonetically spelling out words from other languages. The very first define here is kind of clumsy. It spells out how we would say std. As in ess-tee-dee. The rest of the defines spell out the English pronunciations of the words. I found out about this by way of the following tweet, which showed some C++ written using a substantial amount of Japanese.
While it looks cool, I have a preference of minimizing my use of defines in my C++ code. But I’m also not a native 日本語 speaker. I imagine this provides some advantages for someone that is.
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I’ve been looking at the Samsung FlipSuit cards lately. For the uninitiated, these are cards that one slips into a case that cause the phone to also change the content of its inner and outer screens to match the theme on the card. You can find these for the Galaxy Flip 4/5, and more recently the Galaxy S24. A question I’ve seen asked in reading about these is “How do they work” and “Can I make my own.” While I don’t have sufficient technical data needed to enable you to go off and make your own, I do have some knowledge of how these work. These are not the first iteration of such a system. The earliest form of those date back to 2018.
Galaxy Friends: An Ancestor of FlipSuit
At the Samsung Developer’s Conference from 2018, one of the technologies and solutions on display was Samsung Theme Studio. With Theme Studio, a creative could package changes to the UI to give the phone an entirely new look and feel. These themes are packaged in an APK (like other Android applications) and available for download in the Samsung App Store. This tool is relevant to another offering released that same year.
At the same conference, Samsung showcased the Galaxy Friends Accessory program. Under this program, someone could make an NFC enabled and associate that case with a Theme and other content. The theme would automatically be applied just by putting the case on a phone. In addition to the theme, content and applications could be associated with the case. Someone could get exclusive access to content (that could be changed as frequently as once a day) through having this case. It’s not hard to draw a line between this and the Galaxy FlipSuit cards.
Where can you find the Galaxy Friends program now? I don’t think that you can. The email address associated with it no longer exists. Outside of a few forum posts, there is no mention of it on Samsung’s site at all. The strongest remaining items of evidence that it existed are in the forms of a couple of Amazon listings for Galaxy Friends cases for the Note 10 (Ironman Case, Spiderman Case). Reviews for it make mention of the NFC Chip and the theme that gets applied to the phone.
Does that mean Galaxy Friends is dead and gone? Well, no. Searching for that name yields few results, but searching for the functionality is a different matter.
Knox Configure
Over the years, Samsung has moved its products and services related to device management, configuration, and security under the Knox branding. While you can find some mention of Knox across a broad range of products (don’t be surprised if you find a Wi-Fi enabled clothing washer with Knox) we are most interested in the services on mobile devices. I’ve found that some are confused on what Knox is because of the broad list of products on which it can be found. The specific Knox service in which we have interest is Knox Configure.
Knox Configure provides functionality for enrolling and configuring a device even before it has been removed from its box. A device’s unique ID could be added to someone’s Samsung Knox account (usually through a Samsung reseller). A device could also be enrolled during setup, or enrolled by an accessory. For accessory enrolment, the accessory could be an NFC device, a cover, or a USB device. You might think that NFC devices and covers are identical, but more on that in a moment.
Once enrolled, a device will apply a profile. The profile could contain a variety of settings and applications to be applied to the device. There are two profile attributes of special interest here, the theme and the accessory ID. The theme, according to Samsung’s documentation, would be created by Theme Studio. There’s a bit of a break-down in process and/or documentation here. While Knox Configure points to the Theme Studio page, telling a developer they should get access to it, Theme Studio access is restricted. Years ago, anyone could get access to it. Present day, someone wishing to have access can apply during windows that open every other year (the next window is said to be in 2025). I get the impression that the Knox Configure group in Samsung and the Theme Studio groups are not completely in sync with each other. For those reading this with the hopes of making your own themes, here if your first obstacle.
The accessory ID attributes are meant to be written to the USB, NFC, or cover device. According to Samsung’s current documentation, this is something that should be done by a Samsung Accessory Partner.
These profiles are housed on Samsung’s servers and associated with a licenses that the person making the profile hat to purchase. That these profiles are tied to callbacks to a Samsung services implies that one wouldn’t be able to arbitrarily make their own card without Samsung’s involvement.
There may be other services that Samsung has for distribution of content based on an NFC cards of which I don’t know. Note that Knox is just one of them.
NFC Device Enrollment
How does the NFC device invoke enrollment? One of the messages encoded on an NFC card will be a URL. This URL starts with smdm://accessory (Samsung Mobile Device Management?). This URL will have additionally parameters attached to it. But this URI prefix is important. There is a package that is registered to handle URLs that start with this prefixed. The common name for the package is “Knox Enrollment.” The package identifier is com.sec.enterprise.knox.cloudmdm.smdms. I’ve found that if I use this URL without specifying any parameters that this process will crash and I see output on logcat. I’ve been able to figure out some of the other parameter names, but I have no idea what their potential values would be. Here are some of the other potential parameters passed.
countryiso_code
deviceProductType
email
mdm_token
program
seg_url
service_type
update_url
mdm_token
I speculate that if any information is to be found on potential values for these, that the information will be found in the Knox SDK Documentation. These values get passed to the Knox Enrollment service through this service. Once the device is enrolled, the associated configuration items are applied, including and themes or applications associated with the profile. However, I don’t think that information on all of the values will be found through documentation that is generally avaialble. Samsung explicitly states in one of their documents that only accessory manufacturers can inject the IDs into the accessories.
Image from Samsung documentation stating that only manufacturers can inject identifiers into accessories.
Examining a FlipSuit Card
Though I’ve seen the FlipSuit cards described as NFC cards, I’m not entirely convince of this. When I hold one of these cards to an NFC reading device I get nothing. It is possible that it uses some features of NFC unfamiliar to me. I don’t have either a Flip 5 or Galaxy S24 (the most recent phone that I have my hands on is an S23). Earlier, I mentioned that Knox Config has NFC and covers listed as separate device types. I think this is why, there is something different in the communication from an NFC card and the Flip cards. I held a FlipSuit card to the back of a Galaxy Flip 5 while an NFC examination application was running. I got no info.
What Happens when a Knox Configure License Expires
Knox Configure and cases with themes have been around long enough such that we know what happens when a theme expires. Consider the Galaxy S20 and it’s LED case. The LED case had a theme that was associated with it. That theme expired on or around January 1, 2023. Some users in a reddit thread discussed their experience.Of note, before the theme reached it’s expiration date, there was a notification for it. Note that this notification refers to “Samsung Galaxy Friends.” It’s not clear to me if the theme was expiring because the Galaxy Friends program was being sunset or because the license associated with the theme was at the end of it’s life.
Screen with notification about expiring theme.
When the date was reached, the theme automatically uninstalled.
Notification of Theme Uninstalling.
The Pathway To Making Theme Cards
I’ve mentioned obstacles and information and obstacles. If you still wanted to go through with making a theme card, what would you do? You need to get access to Theme Studio. While the next window for applying for Theme Studio isn’t until 2025, this might not be as much as a problem as some might initially think. Between now and when the window opens, you can start practing designing your themes and get a portfolio put together for the application process. After you have access to Theme Studio and are able to publish themes, you might want to become familiar with Knox Configure. You can get a 90-day subscription to Knox Configure at no cost. You won’t need to get a deep understanding of it though. For making the cards themselves though, you will need to go through a Samsung Accessory Partner. There’s no way around that of which I know, since the information I have on how data is written to the card is incomplete.
Though not in furtherance of making Theme Cards, in one of my next posts, I will be exploring a simple Knox Configuration scenario to customize a Samsung device. I’ll also be posting the code that I used for examining NFC cards. The code was written completely in HTML and JavaScript.
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I have a DSLR that has been modified for Infrared Photography. Digital cameras usually have filters that will block out light that is outside of the visible spectrum. Without these filters, though we cant see this light, the camera’s sensor will still respond to it. If you have an IR remote you can test this out yourself by viewing the emitter end through the camera on your phone and holding down a button on the remote.
The world looks different when you biew the IR or UV light reactions with objects. There are elements of an object that may be invisible until you view them in another spectrum, and elements that might disappear all together. I wanted to explore this more, which is why I have this modified camera. There are a few things that I’ve learned along the way. Once a camera is modified for IR shooting, it’s not very good to use for regular photography. You won’t want to take family photos or vacation pictures with such a modified camera. The viewfinder on the DSLR also becomes useless for some shooting situations; since our eyes cannot see IR light, when some filters are applied to the camera, the view through the viewfinder looks black. Instead, we must enable a live view on the camera’s display to preview the image.
The IR blocking filter being removed from the camera isn’t the only adjustment that needs to be done. Better results come from also adding a filter to the lens that blocks some of the visible colors of light. Post-processing of the photo will be necessary.
I’ve been wanting to take a photograph with the camera for the last week. But obligations to others and my work schedule preventing me from being available for some of the prime hours of the day where the sun would be where I would like for it to be. Today, between meetings, I had a chance to run outside, snap a couple of photographs of a flower, and run back inside. The image that shows at the top of this post is one of the results. That image was taken with a filter on the lens that only lets IR light pass. If I remove the filter, I end up with a picture like the following. Removing the filter and allowing visible light to come through, I get a photo that looks partially desaturated.Though color is present, the influence of the IR on the photo is discernable.
While out at “the farm” I took some pictures of some chickens. As appears to be the case with many things that are red, in infrared they appear closer to white. The chicken’s comb’s look especially white.
I’ll be taking more occasional photographs using this camera. When I do, you’ll generally be able to find them on my Instagram page.
This a lot more for me to learn. I hope to have some interesting shows to post.
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Over the past year, I’ve transitioned some of my devices from conventional to rechargeable batteries. I’ve used rechargeable batteries before and had generally been disappointed with them. The need for a separate charger for each battery type sometimes meant extra hardware to keep up with.
With these batteries, one of the main advantages is that they charge over a USB-C cable. Though they came with USB-A to USB-C cables for charging, I generally use the cables that and power supplies that I already have for my phones.
These don’t last as long as a conventional battery, but I’m okay with that since the charging experience is no-fuss. I often forget to turn off my voice recorder and run through batteries in it quickly. With these, it is less of a concern.
Presently, I’m using AA, AAA, and 9-Volt batteries. You can find all of these on Amazon among other places. The affiliate links for the ones that I purchased are below.
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With some of the free time I had, I decided to remake a video game from my childhood. Though the game was rendered with 3D visuals, it was essentially a 2D game. I’ll need to detect collisions when two actors in the game occupy the same footprint. The footprints will usually be rectangular. But these rectangles could be oriented in any way. Detection of orthognal overlapping bounding boxes is a simple matter of checking if some pointes are within range. But if they are not oriented parallel/perpendicular to each other, then a different check must be done.
Rectangles can be constructed with two triangles. The solution to detecting overlapping rectangles is built upon finding intersection with a triangle. Let’s look at point-triangle intersection first. Let’s visualize some overlapping and non-overlapping scenarios.
Examining this visually, you can intuitively state whether any selected pair of triangles or points intersect with each other. But if I provided you only with the points that make up each triangle, how would you state whether overlap occurs? An algorithmic solution is needed. The two solutions I show here did not originate with me. I found solutions on StackOverflow and RosettaCode. But what I present here is not a copy and past of the solutions. They’ve been adapted some to my needs.
For my points and triangles, I’ll use the following structures.
struct Point
{
float x;
float y;
};
struct Triangle
{
Point pointList[3];
};
There are lots of ways to detect whether a point iw within a triangle. Before writing my own, I found a simple one on GameDev.net. This is an adjusted implementation.
Usage is simple. Passing a point and a triangle to the function pointInTriangle results in the return of a bool value that is true if the point interacts with the triangle.
Having Point-Triangle intersection is great, but I wanted Triangle-Triangle intersection. I decided to use an algorithm from RosettaCode. The code I present here isn’t identical to what was presented there, though. Some adjustments have been made, as I prefer to avoid using explicit pointers to functions. My definition of Triangle and Point are expanded to accomodate the implementation’s use of indices to access the parts of the triangle. By unioning the two definitions, I can use either notation for accessing the members.
struct Point
{
union {
struct {
float x;
float y;
};
float pointList[2];
};
};
struct Triangle
{
union {
struct {
Point p1;
Point p2;
Point p3;
};
Point pointList[3];
};
};
The algorithm makes use of the determinate function, an operation from matrix math. I’m going to skip over explaining the concept of determinants. Explanation of matrix operations deserves its own post.
Another key attribute of this implementation is that it optionally usually enforces the angles of a triangle being provided in a counter-clockwise order. If they are always passed in the same order, there is an opportunity for faster execution of the code. I chose general usability over speed. But I did mark the code with attributes to suggest that the compiler optimize for them being passed in that order.
The original algorithm had a couple of functions that were used to check for boundary collisions or ignore boundary collisions. I have expanded them from 2 functions to 4 functions. Whereas the original structured often as three points that are arbitrarily passed to a function, I prefer to pass triangles as a packaged structure. There is a place in the algorithm where a calculation is formed on a triangle formed by two points of one triangle and one point of the other triangle. The second forms of these functions accept points and will create a triangle from them.
With all of those pieces in place, we can finally look at the part of the algorithm that returns true or false to indicate triangle overlap. The algorithm checks each point of one triangle to see if it is on the interior or external side of each edge of the triangle. If all of the points are on the external side, then no collision has been connected. Then it does the same check swapping the roles of the triangles.If any of the points are not external to the opposing triangle, then the triangles collide.
bool TriangleTriangleCollision(const Triangle& triangle1,
const Triangle& triangle2,
double eps = 0.0, bool allowReversed = true, bool onBoundary = true)
{
//Trangles must be expressed anti-clockwise
CheckTriWinding(triangle1, allowReversed);
CheckTriWinding(triangle2, allowReversed);
//For edge E of trangle 1,
for (int i = 0; i < 3; i++)
{
int j = (i + 1) % 3;
[[likely]]
if (onBoundary)
{
//Check all points of trangle 2 lay on the external side of the edge E. If
//they do, the triangles do not collide.
if (BoundaryCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[0], eps) &&
BoundaryCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[1], eps) &&
BoundaryCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[2], eps))
return false;
}
else
{
if (BoundaryDoesntCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[0], eps) &&
BoundaryDoesntCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[1], eps) &&
BoundaryDoesntCollideChk(triangle1.pointList[i], triangle1.pointList[j], triangle2.pointList[2], eps))
return false;
}
if (onBoundary)
{
//Check all points of trangle 2 lay on the external side of the edge E. If
//they do, the triangles do not collide.
if (BoundaryCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[0], eps) &&
BoundaryCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[1], eps) &&
BoundaryCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[2], eps))
return false;
}
else
{
if (BoundaryDoesntCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[0], eps) &&
BoundaryDoesntCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[1], eps) &&
BoundaryDoesntCollideChk(triangle2.pointList[i], triangle2.pointList[j], triangle1.pointList[2], eps))
return false;
}
}
//The triangles collide
return true;
}
The basic usage of this code is similar to the point collision. Pass the two triangles to the function
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Bottom Line: A rule affecting robo-texting (which is done without a phone) was mistaken for a rule governing/punishing users of T-Mobile phones. T-Mobile has not applied any new fines to customers for their SMS content.
Update 2023 December 31 11:58PM EST
Since I’ve made this posts, there’s been a number of other statements and posts about this misunderstanding that I think are worth considering. The Associated Press published an article about this misunderstanding/misinformation
“The change only impacts third-party messaging vendors that send commercial mass messaging campaigns for other businesses,” the company wrote in a statement emailed to The Associated Press.
Associated Press
There is now a community note under the account of one of the people that accounts for many views of this item of misinformation on Twitter/X.
…Bandwidth the company the user is referring does not provide consumer service. These specific terms of service are for commercial/enterprise users of the T-Mobile network. This does not directly apply to P2P (Peer to peer) messaging.
Twitter/X Community note
There was also a post in the T-Mobile Community forums by a user that received a response from a T-Mobile Community Manager.
These changes only apply to third-party messaging vendors that send commercial mass messaging campaigns for other businesses. The vendors will be fined if the content they are sending does not meet the standards in our code of conduct, which is in place to protect consumers from illegal or illicit content and aligns to federal and state laws.
I watched misunderstanding get legs and spread pretty far during the Christmas holiday weekend. The gist of the misinformation is that T-Mobile is going to fine customers hundreds or thousands of dollars for sending text messages of which T-Mobile doesn’t improved. This misunderstanding appears to be derived from a reading of a Business Code of Conduct, but without an understanding of the terms involved or the partnerships between various companies. I’ll try to explain both in a moment.
Consumer and Non-Consumer Messages
If you have a T-Mobile phone and are sending text messages, those are consumer text messages. If you start a marketing campaign to send out mass SMS messages, create a 2FA service that sends out messages, or are using some other API access, those are non-consumer messages. A basic understanding of how consumer messages works is common, but not so for non-consumer messages. Let’s dig into that a bit more.
Non-Consumer messages are often sent through an API. These messages are sometimes labeled as A2P messages, which means “Application to Person.” The origin of these messages is not a phone. T-Mobile, AT&T, and Verizon provide the ability to post messages into their infrastructure for delivery. How do you get access to this functionality? Generally, you don’t. They don’t let everyone have access to these services. Instead, there are a number of companies with which they establish agreements and have granted access. If you want to use these services, you would establish a connection with one of these companies and they manage many of the other details of what needs to occur. Here are some names of companies that provide such services.
As far as a consumer knows the messages are coming from a 10 digit phone number. These phone numbers may be referred to as A2P 10DLC (Application to Person 10 Digit Long Code). When a new messaging campaign is started, the number associated with the campaign must be registered. The number being registered and associated with an entity, brand, or campaign. Unlike short code messages, if a business also needs to allow customers to call them, they have the option of setting up a voice line associated with the same phone number.
The entities and phone numbers may also be assigned a trust rating. Entities that have a higher trust rating may be granted more throughput on a carrier’s network. If an entity’s trust rating become low, their granted capacity might be lowered or their messages may be disallowed all together. Entities earn a reputation.
What Are These Rules Restricting?
In a nutshell, the rules published by T-Mobile, AT&T, and Verizon disallow text messaging campaigns for unlawful material, including material that may be lawful in some states but not others, scam messages, spam, phishing attempts and impersonation. Some carriers may specifically call out other types of material, but the same general characterization of restrictions apply. The following is what was posted by Bandwidth about the notice (Update 2024 January 2: Bandwidth.com has since restricted viewing the notice. A screenshot of the notice can be viewed here).
T-Mobile is instituting three new fees for non-compliant A2P traffic sent by non-consumers that result in a Severity-0 violation. A Sev-0, (Severity-0) represents the most harmful violation to consumers and is the highest level of escalation with which a carrier will engage with Bandwidth. This applies to all commercial, non-consumer,A2P products (SMS or MMS Short Code, Toll-Free, and 10DLC) that traverse T-Mobile’s network.
With what I’ve shared so far, you may be able to recognize this as something that is not directed at regular customers that are using T-Mobile. The false information I encountered on the change misidentifies the affected partiers as subscribers of the phone service. Let’s dig into what a Sev-0 violation is.
Phishing messages that appear to come from reputable companies
Depictions of violenge, messages engaging in harassment, defamation, deception, and fraud
Adult Material
High-Risk content that generates a lot of user complaints, such as home offers, payday loans, and gambling content.
Sex, Hate, Alcohol, Firearms, and Tabaco related content (SHAFT)
There is other content in this category. The above isn’t exhaustive.
Bandwidth list as having the highest fees messages related to phishing and social engineering at 2,000 USD per violation. Second, at a 1,000 USD fine is unlawful content such as controlled substances or substances not lawful in all 50 states. The lowest fine that Bandwidth mentions is 500 USD is for violations of SHAFT or messages that don’t follow state or federal regulations.
Overall, this looks to be a move that may motivate A2P partners to make more efforts to filter out certain type of content that is at least generally annoying if not worst.
What About the Other Carriers?
In the USA there are three nation-wide carriers. AT&T, T-Mobile, and Verizon offer service across the nation. I don’t know if Verizon or AT&T have fines associated with violations, but they do have a code of conduct for A2P providers. If you’d like to read their code of conduct documentations, you can find them here.
There’s a lot of overlap in their rules. This may come as no surprise, especially to those familiar with CTIA. CTIA is a wireless trade organization representing carriers in the USA, supplies, and manufacturers of wireless products. They have been around since the mid-1980s. Current members of CTIA include AT&T, T-Mobile, Verizon, and US Cellular. You can find a list of members here.
There is a lot more that could be said about how these messaging services work. I may detail it further one day. But for now, the main take-away is that there’s a popular misconception about the changes that T-Mobile is said to be implementing that are recognized as a mistaken interpretation once one has a casual familiarity with some of the terms involved.
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j2i.net 
