cryptanalysis question: Does knowing some of the content of the message make the full message vulnerable to decryption?

[Faramir]

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El 30-01-2014 18:15, Donald Morgan Jr. escribió:
> If you know a user has a signature that they use to always end a
> message with, does that data aid in the decryption of the file?
> Would this exploit be applicable to symmetric encryption methods as
> well?

  I think padding helps to avoid that, but I'm not sure if gpg uses
padding at the symmetric encryption step.

  Best Regards

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