Erron Criddle writes:
Regarding the 2 octet checksum (that is encrypted), how do we encrypt:
encrypt (Secret MPI's) + encrypt (2 octet checksum)
encrypt (Secret MPI's + 2 octet checksum)
I'm not sure what distinction you are trying to draw here. Presumably
"+" refers to concatenation? With CFB mode you have the effect of a
stream cipher, hence there is no difference between encrypt(a+b) and
Also, I am also assuming a 16 bit checksum is:
16 bit checksum = 16 most significant bits (sum of Secret MPI's ASCII
values MOD 65536)
I'm not sure what you mean by the 16 "most significant" bits of a value
which is mod 2^16. That's just a 16 bit value.
These are not ASCII characters (ASCII is a mapping between typographic
symbols like letters, and binary values). They are simple binary octets.
this also assumes a big endian system.
Yes, the 16 bit value is taken in big endian form, i.e. high byte,
then low byte. This is the general convention in OpenPGP, as noted in