Crypto.PubKey.DH

Represent Diffie Hellman parameters namely P (prime), and G (generator).

Represent Diffie Hellman public number Y.

Represent Diffie Hellman private number X.

Represent Diffie Hellman shared secret.

generate params from a specific generator (2 or 5 are common values) we generate a safe prime (a prime number of the form 2p+1 where p is also prime)

generate a private number with no specific property this number is usually called X in DH text.

calculate the public number from the parameters and the private key this number is usually called Y in DH text.

calculate the public number from the parameters and the private key this number is usually called Y in DH text.

DEPRECATED use calculatePublic

generate a shared key using our private number and the other party public number

This raises the CryptoError that tryGetShared reports. Use tryGetShared where the failure has to be handled.

generate a shared key using our private number and the other party public number, reporting a rejected public number instead of raising.

The public number comes from the other party, so it is checked to satisfy 1 < y < p-1 as RFC 7919 section 5.1 requires. The excluded values generate the subgroup {1} or {1, p-1}, so the shared secret they produce is one of a handful of constants and carries none of our private number's secrecy. A value outside that range is reported as CryptoError_ParameterInvalid.

Note this is the only check made here: it does not establish that y lies in the subgroup generated by g, which needs the subgroup order that Params does not carry.