2009/2/17 Victor Duchovni <victor.ducho...@morganstanley.com>: > On Mon, Feb 16, 2009 at 01:48:54PM +0800, loody wrote: > >> Dear all: >> I want to realize aes, so I trace enc_main in enc.c. >> But I find there are a lot call back functions such that I spend more >> time on tracing these call back functions than understanding aes >> algorithm. >> >> I have studied the aes flow chart on the wiki, >> http://en.wikipedia.org/wiki/Advanced_Encryption_Standard >> But I cannot find out where the connection between the password I >> input with the aes. >> >> suppose I type: >> openssl enc -aes-256-cbc -salt -in test.txt -out test.enc >> enter aes-256-cbc encryption password: 123456 >> Verifying - enter aes-256-cbc encryption password:123456 >> >> How do we deal with "123456" before calling AES_cbc_encrypt? >> Is "123456" a part of key? > > User-supplied passwords (password based encryption) are not strong > enough to use directly as AES keys. Instead these are passed to > a key-derivation function. OpenSSL uses PBKDF2 from PKCS#5 v2.1 > > http://en.wikipedia.org/wiki/PBKDF2 > > The API entry point (still to be documented) is: > > src/distro/crypto/evp/p5_crpt2.c: > PKCS5_PBKDF2_HMAC_SHA1(pass, passlen, salt, saltlen, iter, keylen, key)
Hi: thanks for your help. I have another questions about aes: The round# is set according to the bits we pass to AES_set_encrypt_key. And Nk*round# keys are also produced well in it. But how about Nb, the number of column in state? (in 128, 192 and 256 bits block plaintext, the Nb, column# of state is 4,6,8.) The parameters we pass to AES_encrypt are in, out, key. We don't tell AES_encrypt the total bits of plaintext. If we don't pass bis length information to AES_encrypt, how it do the SubBytes, ShiftRows, MixColumns and AddRoundKey? appreciate your help, miloody ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
