What exact default Encryption Algorithm (symmetric cipher) is used?

Asked by frankii

I have looked throughout the related Mailing-List [1] and Duplicity [2] website and I cannot see any citation or reference to the exact default Encryption Algorithm (symmetric cipher) that is used for Duplicity. The website does link to:

http://www.gnupg.org/gph/en/manual.html#AEN185

but this 1999 document is just a general discussion about symmetric ciphers, it does not indicate which exact symmetric cipher Duplicity uses. I think it somewhat puzzling that this information is very hard to find and can't understand why?

I am using Deja Dup with Duplicity so reliant on it's default symmetric cipher setting, but it's website [3] also does not indicate which exact default Encryption Algorithm (symmetric cipher) is used.

Apologies if the answer is posted on the websites listed below, but I can't find the answer to something that needs prominence when Encryption is such a critical function.

[1] http://lists.nongnu.org/mailman/listinfo/duplicity-talk
[2] http://duplicity.nongnu.org/
[3] http://live.gnome.org/DejaDup

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frankii (frankltd) said :
#1

Is the cipher AES, DES, Blowfish? What size is the key? Could it be a 56-bit key, 128-bit key or 256-bit? This technical information is important as it would indicate whether the type and bit size of the cipher is or is not secure from being easily cracked.

The answer to these very specific questions is not found at:
              http://www.gnupg.org/gph/en/manual.html#AEN185

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Plamen K. Kosseff (p-kosseff) said :
#2

As far as I know gnupg is uses for both asymmetric and symmetric encryption. So the algorithm will be whatever gnupg is configured to use.

But I'm not 100% sure.

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Michael Terry (mterry) said :
#3

The default for GPG appears to be CAST-128 (aka CAST5): https://secure.wikimedia.org/wikipedia/en/wiki/CAST-128

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frankii (frankltd) said :
#4

I have found the answer is listed explicitly online:

"The default symmetric cipher used is CAST5"
http://www.gnupg.org/documentation/manuals/gnupg/Operational-GPG-Commands.html