3 ms·

I just made a short (2048 bit) key pair, and made the public key into a QR Code (as ascii armoured text, so it could have been more dense in straight binary) h

I just made a short (2048 bit) key pair, and made the public key into a QR Code (as ascii armoured text, so it could have been more dense in straight binary) https://flic.kr/p/2cYCwfG https://flic.kr/p/2cYCwfG I could only get it into a 141x141 by dropping error correction right down to 7%, but under ideal conditions (from my monitor to an iPhone) it reads reliably, as shown. I tried a 4096 bit key, but I couldn't (as text) get it into even a 171x171 QR Code at minimum error correction without truncating (and even in ideal conditions, my phone won't reliably read 171x171 resolution QR codes...)

mcpherrinm 8y ago
RSA keys are significantly larger than elliptic curve keys, so for something like putting a pubkey in a QR code, you're much better off going with a 256 bit elliptic curve key than any other hacks to try shave bytes off encoding RSA keys.
ryan-c 8y ago
Some friends and I experimented with this when running a CTF a few years back. We figured out that setting some of the Chinese Remainder Theorem values in the private key to zero, we could stuff it into a QR code and read it when printed using a receipt printer.