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Re: Please Help with OpenPGP's CFB Mode

2003-04-07 10:11:20

Daniel Fabian writes:
- I load the FR with c2 - c17:
- Encrypt it: FRE: 121;156;77;216;12;149;25;199;12;206;220;6;43;173;198;65;
- And get the WRONG plaintext block

This is definitly not the UTF-8 representation of "The MD5 hash alg".
Could someone please tell me what I'm doing wrong?

You have done the decryption properly.  Your plaintext when expressed
in hex form is:

c8 35 01 3b 6d 52 c2 c0 c8 c0 c0 10 92 91 aa e0

You have to interpret this as PGP data per RFC2440.  C8 is the tag byte
for a Compressed Data Packet (see section 5.6).  35 is its length.  01 is
the type of compression, namely ZIP (see section 9.3).  The remaining
data is to be input to the decompression algorithm.  The output of that
will be a PGP Literal Data Packet, and the contents of that packet will
include your text.

Hal Finney

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