gen_key.rn

//  Copyright 2021 Google LLC.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

if argv.length() != 2 {
  throw "Usage: gen_key <prime(hex)>"
}
p = argv[1].fromHex().toUintBE(u2048)
privateKey = rand2048 % p
g = 2u2048  // Group generator.  Using 2 is fine, modulo a prime.
publicKey = reveal(g^privateKey mod p)
println "privateKey=", reveal(privateKey.toStringBE().toHex())
println "publicKey=", publicKey.toStringBE().toHex()