On Mar 27, 2012 12:55 AM, "Daniel Shahaf" <d...@daniel.shahaf.name> wrote: >... > > On 27.03.2012 05:23, Greg Stein wrote: > > >... > > > While discussing this on IRC some, I did think of one case where you > > > want to know they got the correct master passphrase: when they are > > > updating a server's password. A mis-entry could completely garble the > > > stored/encrypted contents. > > Don't ew have some other ways of addresing that use-case? Such as, say, > encrypting a random string, and at decrypting compare the decrypted > text's sha1 to the value computed at encryption time?
There ya go. I knew we could tease out a solution. That sounds good to me. So, for each password, we store two more 16-byte blocks of encrypted data, and a SHA1 has (20 bytes). At decrypt time, we also decrypt those blocks, hash the 32 byte result, and compare against the hash. I would also suggest that we append those two blocks to the padded password, so they get the advantage of CBC, without needing to pick a second IV. Cheers, -g
