How to Give Persistent Names To USB-Serial Devices on Ubuntu 14.04
When your dock reshuffles ttyUSB assignments, Tayyar shows how to bind USB-serial devices to persistent names on Ubuntu 14.04. The post walks through using dmesg and udevadm to locate unique attributes like KERNELS and ATTRS{serial}, creating /etc/udev/rules.d entries with NAME and SYMLINK, and applying rules with udevadm trigger. It includes common pitfalls and quick fixes to get minicom talking to the right port.
Mathematics and Cryptography
Cryptographic math can look intimidating, but this roundup trims it to what FPGA engineers actually need. It groups concise articles on number theory and elliptic curves, focusing on polynomial math over Galois fields, FPGA-friendly inversion and one-clock-cycle techniques, and elliptic-curve key exchange and digital signatures. Read this to learn which subroutines to implement first and how to turn math into Verilog or VHDL.
Elliptic Curve Digital Signatures
Elliptic curve digital signatures deliver compact, strong message authentication by combining a hash of the message with elliptic curve point math. This post walks through the standard sign and verify equations, showing why recomputing a point R' yields the same x coordinate only when the hash matches. It also explains the Nyberg-Rueppel alternative that removes modular inversion and an FPGA-friendly trick of transmitting point D to avoid integer modular arithmetic.
Elliptic Curve Key Exchange
Elliptic Curve key exchange gives a fresh secret for every session so past messages stay safe even if one key is discovered. This post walks through an ElGamal-style ephemeral exchange and the MQV protocol, showing how MQV mixes static and random keys to provide mutual authentication and forward secrecy. It also explains how MQV can be implemented using only curve operations to save FPGA area and why erasing ephemeral values matters.
Polynomial Inverse
One of the important steps of computing point addition over elliptic curves is a division of two polynomials.
One Clock Cycle Polynomial Math
Error correction codes and cryptographic computations are most easily performed working with GF(2^n)
Elliptic Curve Cryptography
Secure online communications require encryption. One standard is AES (Advanced Encryption Standard) from NIST. But for this to work, both sides need the same key for encryption and decryption. This is called Private Key encryption.
Polynomial Math
This post walks through squaring and inversion in a tiny finite field to make ECC math tangible. Using GF(2^5) with primitive polynomial beta^5 + beta^2 + 1 it shows why squaring cancels cross terms so you only need half the lookup table, and how Fermat exponentiation computes inverses via repeated squarings and multiplies. It also demonstrates the Extended Euclid polynomial inverse and compares FPGA and CPU tradeoffs.
Number Theory for Codes
If CRCs have felt like black magic, this post peels back the curtain with basic number theory and polynomial arithmetic over GF(2). It shows how fixed-width processor arithmetic becomes arithmetic in a finite field, how bit sequences are treated as polynomials, and why primitive polynomials generate every nonzero element. You also get practical insights on CRC implementation with byte tables and LFSRs.
The CRC Wild Goose Chase: PPP Does What?!?!?!
Jason Sachs walks through a CRC rabbit hole and explains why ambiguous CRC names and incomplete specs lead to subtle protocol bugs. He demonstrates how XMODEM and KERMIT variants with a zero initial value can miss dropped leading-zero bytes, praises the X.25 standard for providing test vectors and a clear CRC16 definition, and warns that RFCs that ship only sample code are a poor substitute for a proper specification.
Linear Feedback Shift Registers for the Uninitiated, Part XII: Spread-Spectrum Fundamentals
Jason Sachs shows why LFSR-generated pseudonoise is a natural fit for direct-sequence spread spectrum, then walks through Fourier basics, spectral plots, and runnable Python examples. The article demonstrates how DSSS multiplies a UART bitstream with a chipping sequence to spread energy, how despreading concentrates the desired signal while scrambling narrowband interference, and how multiple transmitters can share bandwidth when using uncorrelated sequences.
Polynomial Inverse
One of the important steps of computing point addition over elliptic curves is a division of two polynomials.
Reverse engineering wireless wall outlets
Fabien Le Mentec reverse engineers a cheap set of wireless wall outlets to add them to his BANO home automation while avoiding uncertified mains hardware. He uses PCB inspection to identify a Holtek MCU and RF83C, captures 433.92 MHz OOK signals with an RTL-SDR and ookdump, then replays commands using an RFM22 in direct mode controlled by an ATmega328P. The post explains frame structure and links to a working GitHub implementation.
Using a RTLSDR dongle to validate NRF905 configuration
I am currently working on a system to monitor the garage door status from my flat. Both places are 7 floors apart, and I need to send the data wirelessly. I chose to operate on the 433MHz carrier, and I ordered 2 PTR8000 modules: http://www.electrodragon.com/w/NRF905_Transceiver_433MHz-Wireless_ModuleThe PTR8000 is based on the dual band sub 1GHz NRF905 chipset from NORDICSEMI: http://www.nordicsemi.com/eng/Products/Sub-1-GHz-RF/nRF905I...Elliptic Curve Cryptography - Multiple Signatures
Point pairings let you compress many independent elliptic-curve signatures into a single verification, reducing n checks to one. This post explains how each signer derives a coefficient from the ordered list of public keys, aggregates signatures on the base group and public keys on the extension group, and verifies everything with one pairing computation. It also flags practical cautions like key validation and agreed ordering.
One Clock Cycle Polynomial Math
Error correction codes and cryptographic computations are most easily performed working with GF(2^n)
Polynomial Math
This post walks through squaring and inversion in a tiny finite field to make ECC math tangible. Using GF(2^5) with primitive polynomial beta^5 + beta^2 + 1 it shows why squaring cancels cross terms so you only need half the lookup table, and how Fermat exponentiation computes inverses via repeated squarings and multiplies. It also demonstrates the Extended Euclid polynomial inverse and compares FPGA and CPU tradeoffs.
Mathematics and Cryptography
Cryptographic math can look intimidating, but this roundup trims it to what FPGA engineers actually need. It groups concise articles on number theory and elliptic curves, focusing on polynomial math over Galois fields, FPGA-friendly inversion and one-clock-cycle techniques, and elliptic-curve key exchange and digital signatures. Read this to learn which subroutines to implement first and how to turn math into Verilog or VHDL.
Bellegram, a wireless DIY doorbell that sends you a Telegram message
A wireless button that uses the M5 STAMP PICO and Mongoose to send a Telegram message when pressed. The code is written in C
Elliptic Curve Digital Signatures
Elliptic curve digital signatures deliver compact, strong message authentication by combining a hash of the message with elliptic curve point math. This post walks through the standard sign and verify equations, showing why recomputing a point R' yields the same x coordinate only when the hash matches. It also explains the Nyberg-Rueppel alternative that removes modular inversion and an FPGA-friendly trick of transmitting point D to avoid integer modular arithmetic.
Getting Started With Zephyr: Bluetooth Low Energy
In this blog post, I show how to enable BLE support in a Zephyr application. First, I show the necessary configuration options in Kconfig. Then, I show how to use the Zephyr functions and macros to create a custom service and characteristic for a contrived application.
On hardware state machines: How to write a simple MAC controller using the RP2040 PIOs
Hardware state machines are nice, and the RP2040 has two blocks with up to four machines each. Their instruction set is limited, but powerful, and they can execute an instruction per cycle, pushing and popping from their FIFOs and shifting bytes in and out. The Raspberry Pi Pico does not have an Ethernet connection, but there are many PHY boards available… take a LAN8720 board and connect it to the Pico; you’re done. The firmware ? Introducing Mongoose…
Elliptic Curve Key Exchange
Elliptic Curve key exchange gives a fresh secret for every session so past messages stay safe even if one key is discovered. This post walks through an ElGamal-style ephemeral exchange and the MQV protocol, showing how MQV mixes static and random keys to provide mutual authentication and forward secrecy. It also explains how MQV can be implemented using only curve operations to save FPGA area and why erasing ephemeral values matters.
Elliptic Curve Cryptography - Security Considerations
The security of elliptic curve cryptography is determined by the elliptic curve discrete log problem. This article explains what that means. A comparison with real number logarithm and modular arithmetic gives context for why it is called a log problem.
Picowoose: The Raspberry Pi Pico-W meets Mongoose
This example application describes the way to adapt the George Robotics CYW43 driver, present in the Pico-SDK, to work with Cesanta's Mongoose. We are then able to use Mongoose internal TCP/IP stack (with TLS 1.3), instead of lwIP (and MbedTLS).
Polynomial Math
This post walks through squaring and inversion in a tiny finite field to make ECC math tangible. Using GF(2^5) with primitive polynomial beta^5 + beta^2 + 1 it shows why squaring cancels cross terms so you only need half the lookup table, and how Fermat exponentiation computes inverses via repeated squarings and multiplies. It also demonstrates the Extended Euclid polynomial inverse and compares FPGA and CPU tradeoffs.
When a Mongoose met a MicroPython, part I
This is more a framework than an actual application, with it you can integrate MicroPython and Cesanta's Mongoose.
Mongoose runs when called by MicroPython and is able to run Python functions as callbacks for the events you decide in your event handler. The code is completely written in C, except for the example Python callback functions, of course. To try it, you can just build this example on a Linux machine, and, with just a small tweak, you can also run it on any ESP32 board.
Elliptic Curve Digital Signatures
Elliptic curve digital signatures deliver compact, strong message authentication by combining a hash of the message with elliptic curve point math. This post walks through the standard sign and verify equations, showing why recomputing a point R' yields the same x coordinate only when the hash matches. It also explains the Nyberg-Rueppel alternative that removes modular inversion and an FPGA-friendly trick of transmitting point D to avoid integer modular arithmetic.
Elliptic Curve Cryptography - Extension Fields
An introduction to the pairing of points on elliptic curves. Point pairing normally requires curves over an extension field because the structure of an elliptic curve has two independent sets of points if it is large enough. The rules of pairings are described in a general way to show they can be useful for verification purposes.
STM32 B-CAMS-OMV Walkthrough
Want to prototype embedded vision quickly? This walkthrough shows how the STM32 B-CAMS-OMV camera module pairs with the STM32H747I-DISCO discovery kit and the FP-AI-VISION1 function pack to get you running in minutes. The video covers the camera connection interface, key software functions to control and process data, and the ISP features that let image processing run inside the camera. The STM32 H7 project with B-CAMS-OMV drivers is available on GitHub.
