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Date: Mon, 05 Mar 2012 21:00:26 +0100
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: AES decrypt portions to buffer (for RAR format)

Could anyone help me with this trivial OpenSSL question. I can't find
the docs (wtf?) nor any google example. Maybe I'm just too exhausted. I
want to decrypt 32KB or so at a time from a larger buffer of encrypted data.

This works fine (all at once):

 AES_KEY key;
 AES_set_decrypt_key(aes_key, 16 * 8, &key);
 AES_cbc_encrypt(input, output, len, &key, aes_iv, AES_DECRYPT);


This is what I think I'm doing and it produces garbage from 2nd read on
(actually that is a presumtion, I only know the end result is bad):

 AES_KEY key;
 AES_set_decrypt_key(aes_key, 16 * 8, &key);
 while(data to read) {
   AES_cbc_encrypt(input, output, BUF_SIZE, &key, aes_iv, AES_DECRYPT);
   ...process buffer and increment input pointer...
  }

Are not &key and/or aes_iv supposed to keep state? Or should I call
set_key each time, or what?

magnum

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