Exec Error Warning: This messages modification detection code does not match the message. This means it is likely the message has been changed since the time it was encrypted.

Rachel Willmer rwillmer at gmail.com
Mon Apr 21 12:50:29 CEST 2008


On 21/04/2008, Hicks, Paul <Paul.Hicks at sensis.com.au> wrote:
>
>  Hello,
>
>
>
> I'm hoping someone may be able to help us interpret the following error
> message:
>
>
>
> *Exec Error Warning: This messages modification detection code does not
> match the message.  This means it is likely the message has been changed
> since the time it was encrypted.*
>

The "Modification Detection Code" is a OpenPGP packet which is created at
the time of encryption, which contains a SHA-1 hash of the plaintext data.
It is analagous to a checksum, and is encrypted together with the plaintext.

What the error message is saying (I think) is that the decryption process
which you're running is recreating that hash from the plaintext it has
found, and it doesn't match the original hash (which it should).

Sections 5.13 and 5.14 of RFC 4880 talk about the use of the MDC packet in
more detail.

HTH
Rachel
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