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I'm trying to crack an encrypted data stream. It appears to be using a 64-bit 3DES key (as written in the application logs), and in fact using that key does correctly decrypt the first 64-bit packet sent.

Where I'm getting confused, is it absolutely will not decrypt the second one sent.

Added examples:

key = d7 a0 f3 70 82 6c b0 ff
ct1 = 63b8ea10e5ec3424
ct2 = 03b02e2d20b611b2

--

key = 08 aa 25 d5 5e fa 59 55
ct1 = 3794fbb20c2d25c2
ct2 = bfdbd05fedfcc749
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There is no such thing as 64 bit triple DES. Well, to be more precise, there is, but it is fully equivalent to single DES. If the first block decrypts and the rest doesn't then you're probably using the wrong mode of operation. Try a few others such as DES in CBC mode or CTR mode using a zero valued IV.

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