Thank you - I understand what you are saying about Domain parameters, but I think I have solved my initial query. I believe A can be pre-computed before Bob has even entered the picture, and it appears CryptoPP does just that. In ElGamalKeys::PublicKey, I found a parameter calle "PublicElement" that corresponds to the A, i.e. it is, in CryptoPP terms:
A(PublicElement) = SubgroupGenerator^PrivateExponent mod Modulus so I need not access Alice's private key in order to extract the parameters for "manually" performing ElGamal encryption from Bob to Alice, I have everything I need to do it from the PublicKey from the beginning. Thanks, -Derek On Monday, September 11, 2017 at 11:21:38 PM UTC-4, Jeffrey Walton wrote: > > > > On Monday, September 11, 2017 at 10:01:41 PM UTC-4, Derek Cole wrote: >> >> Hello, >> >> I have been trying to learn ElGamal encryption by way of this site: >> >> https://cryptographyacademy.com/elgamal/ >> >> I am able to find the SubgroupOrder, SubgroupGenerator, and Modulus of an >> ElGamalKeys::PublicKey, but I am unable to find the 3rd parameter of the >> PublicKey which is computed using Alice's private exponent. According to >> the site: >> >> Next Alice chooses the secret key sk=a between 1 and p−1 and computes >>> A=g^a mod p >>> >> Alice then publish the public key pk=(p,g,A). >>> >> >> So how do I find the A parameter from the PublicKey? >> > > I believe A is a domain parameter. Alice and Bob have to agree to use them > before any instance of a protocol is run. > > The equivalent problem in elliptic curves is, how do you know which field > you are working in. That's why you have named curves like NIST P-256. The > name P-256 conveys the domain parameters we need to execute an instance of > the protocol. > > My apologies if I mis-parsed the question. > > Jeff > -- -- You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to cryptopp-users-unsubscr...@googlegroups.com. More information about Crypto++ and this group is available at http://www.cryptopp.com. --- You received this message because you are subscribed to the Google Groups "Crypto++ Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to cryptopp-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
