distinguishing gnupg and pgp messages encrypted to rsa v4 keys

[vedaal at hush.com]

if someone uses compression algo 1,
and encrypts a message to an rsa v4 key,
using a 256 bit algorithm,

{and leaves out the version line ;-) }

is it possible to determine that the message was encrypted using gnupg
and not pgp 8?

pgp 8 will also have the mdc protection.

(it is trivial to tell the difference for a dh key, 
but is there a simple way for an rsa v4 key?
i.e. 
any tell-tale sign in gpg list packets, or pgp dump?)

tia,

vedaal





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