2025-01-11
RT bk2204:
This factorization of a 512-bit DKIM key is quite interesting and shows why small keys are a problem.
3072 bits is the appropriate minimum size for RSA keys these days, although some people try to get away with 2048-bit keys. I do still routinely see lots of 1024-bit keys for DKIM, though.
https://dmarcchecker.app/articles/crack-512-bit-dkim-rsa-key