DISQUS

Matasano Chargen: RSA Signature Forgery Explained (with Nate Lawson) - Part II

  • Halvar · 3 years ago
    Silly question, but couldn't the entire thing have been avoided had we

    a) switched to OAEP ?
    b) implemented OAEP correctly ?
    c) refused to trust anyone who uses a low exponent ?

    At least, if we trust the random oracle model, we have something relatively strong in our hands (OAEP). I am consistently surprised that the migration away from other, clearly weaker message padding schemes isn't happening more quickly.

    Cheers,
    Halvar
  • tyme · 3 years ago
    I'd love to hear an explanation for why the people in charge of the TLS standard haven't added any ciphersuites with alternative hashes.

    They add a screwball symmetric algorithm like SEED, yet they can't be bothered to add suites that use SHA-256, SHA-512, Whirlpool, or Tiger, even when there was speculation that SHA-1 would be next to fall when MD5 attacks were announced a couple years ago?
  • Thomas Ptacek · 3 years ago
    MD5 makes this attack very slightly easier. SHA256 would make it slightly harder (you'd have a harder time sliding a bogus hash into a 1024 bit modulus). But all the engineering you could do with hash functions are for nothing if you don't get signature verification right.