RFID Card Cloner
I decided to make my own RFID card reader and writer to clone / store my own RFID cards to some blanks, in case I lost my originals. As this was a fairly simple task, I decided to use an ESP32 I had for it's easy, fast development directly from my PC, and strong support for the RFID reader/writing I chose.
This was not a particularly polished product and was never designed to be long term, so a simple breadboard circuit and jumper wires was plenty sufficient.
I found an existing module online for the ESP32 with support for my particular card reader that worked perfectly after writing some simple scripts to read, write and clone my cards.
The cards themselves are special cards that are unlocked to be both readable and writable. Many cards sold are in fact not completely re-writable, with certain sections of the card still locked and read only. The most common variety of this is "block zero", with cards often stating if they support rewriting block zero or not. Block zero contains the serial number of the tag, also known as a Unique Identifier or UID, and is a bit of a grey area as to whether this is allowed or not, however, they are easily purchased and this was used solely for personal use.