Steve/Victor,

>You mean you want to do:
>SHA1(A)
>and later do:
>SHA1(A || B)
>without including A again?

That is correct. Thats exactly what I want to do.

>You need to serialize, save and restore the intermediate state of
>the digest before you call "final" if you need to be able to append
>more data without re-computing the entire checksum.

I am open to the idea of serializing, saving and restoring.

> OpenSSL does not provide a serialization interface for MD_CTX objects.
> Perhaps you're better off with a simpler library that does not support
> engines, and other features that make serialization difficult.

Both of you mention that OpenSSL doesn't provide such an interface. May be
this question is not appropriate for this forum, but do you know of any such
simpler libraries that I might be able to use?

Has anyone else on this forum ran in to a similar situation and had to dive
deep in to the source code to make this work?

Thanks a lot for the prompt response!

Subra

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