require 'digest' require 'openssl' module SRP module Util # constants both sides know # in this case taken from srp-js PRIME_N = <<-EOS.split.join.hex 115b8b692e0e045692cf280b436735c77a5a9e8a9e7ed56c965f87db5b2a2ece3 EOS BIG_PRIME_N = <<-EOS.split.join.hex # 1024 bits modulus (N) eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c25657 6d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089da d15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e5 7ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb 06e3 EOS GENERATOR = 2 # g # a^n (mod m) def modpow(a, n, m) r = 1 while true r = r * a % m if n[0] == 1 n >>= 1 return r if n == 0 a = a * a % m end end # Hashes the (long) int args def sha256_int(*args) sha256_hex(*args.map{|a| a.to_s(16)}) end # Hashes the hex args def sha256_hex(*args) h = args.join('') sha256_str([h].pack('H*')) end def sha256_str(s) Digest::SHA2.hexdigest(s) end def bigrand(bytes) OpenSSL::Random.random_bytes(bytes).unpack("H*")[0] end def multiplier @k ||= calculate_multiplier end protected def calculate_multiplier # GENERATOR hex needs to be prefixed with 0 so it's not "2" -> 32 ghex = '0%x' % GENERATOR sha256_hex(BIG_PRIME_N.to_s(16), ghex).hex end def calculate_m(aa, bb, s) sha256_int(aa, bb, s).hex end def calculate_u(aa, bb) sha256_int(aa, bb).hex end end end