syntax = "proto3";
package zkp_protocol;

/*
 * Prover registers in the server sending:
 * y1 = alpha^x mod p
 * y2 = beta^x mod p
 */ 
message RegisterRequest {
    string user = 1;
    bytes y1 = 2;
    bytes y2 = 3;
}

message RegisterResponse {}

/*
 * Prover ask for challenge in the server sending
 * r1 = alpha^k mod p
 * r2 = beta^k mod p
 * Verifier sends the challenge "c" back
 */ 
message AuthenticationChallengeRequest {
    string user = 1;
    bytes r1 = 2;
    bytes r2 = 3;
}

message AuthenticationChallengeResponse {
    string auth_id = 1;
    bytes c = 2;
}

/*
 * Prover sends solution "s = k - c * x mod q" to the challenge
 * Verifier sends the session ID if the solution is correct
 */ 
message AuthenticationAnswerRequest {
    string auth_id = 1;
    bytes s = 2;
}

message AuthenticationAnswerResponse {
    string session_id = 1;
}

service Auth {
    rpc Register(RegisterRequest) returns (RegisterResponse) {}
    rpc CreateAuthenticationChallenge(AuthenticationChallengeRequest) returns (AuthenticationChallengeResponse) {}
    rpc VerifyAuthentication(AuthenticationAnswerRequest) returns (AuthenticationAnswerResponse) {}
}