-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 23/08/13 09:53, DC wrote: > One difficult problem in public-key encryption is key exchange: how > to get a recipient's public key and know it's really theirs. My > plan is to make make your email the hash of your public key. For > example, my address is *nqkgpx6bqscsl...@scramble.io (I borrowed > this idea from Tor Hidden Services.)
Hi DC, The simple, usable interface is really cool, I love it. Obligatory crypto bikeshedding: An 80-bit hash isn't long enough to prevent a second-preimage attack by a well-funded adversary, but it's too long for users to memorise or manually enter addresses. Perhaps a longer hash would be better? When storing the private key on the server, you encrypt the private key with a symmetric key derived from the user's passphrase. The server could use a dictionary attack with rainbow tables to decrypt the private key. You should use random salt and a key derivation function designed for deriving keys from passwords, such as PBKDF2 or scrypt, to derive the symmetric key. How exactly is the symmetric key used to encrypt the private key? What block cipher mode do you use? Is there authentication as well as encryption? Cheers, Michael -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBAgAGBQJSF2aRAAoJEBEET9GfxSfMgikIAJeU459ig7XNufyyIuO9BAUF /J0pd0g+pPspWoHvby8W6A1g0ZbTsGBVMbuEOx9BKuSA1FY1skLGZ+Ua6LZUX1ZQ uLNHFs5+kP5lNelYw2oZp/QI63HExAgjMzrFryRl9/pC3Q49N/jdlN+Ssh5YHZ47 LhPNOtgZP4jTq3//T11f7T3fQ09PALrpgREGagfybfP598sEmLuQ2iA2kZNYWO/9 vSnYnQBaWXtmissF0znaOPELYlGGW/TMZMGWxSJ748pjpWB6fZR3/IlRXTaMrp76 8MVhjQP6MCi5AJpsDserQWscTaQyDTP/g7ZVGshreOFelPGjB4QwhFlBfjBEzr0= =k3QU -----END PGP SIGNATURE----- -- Liberationtech is a public list whose archives are searchable on Google. Violations of list guidelines will get you moderated: https://mailman.stanford.edu/mailman/listinfo/liberationtech. Unsubscribe, change to digest, or change password by emailing moderator at compa...@stanford.edu.
