From 2b52444043b26a01cc1eb82c456e325916e25194 Mon Sep 17 00:00:00 2001 From: siddharth Date: Sun, 21 Nov 2021 18:45:53 -0500 Subject: lib: implement diffie-hellman --- lib/dh.go | 41 +++++++++++++++++++++++++++++++++++++++++ lib/dh_test.go | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 77 insertions(+) create mode 100644 lib/dh.go create mode 100644 lib/dh_test.go (limited to 'lib') diff --git a/lib/dh.go b/lib/dh.go new file mode 100644 index 0000000..0782033 --- /dev/null +++ b/lib/dh.go @@ -0,0 +1,41 @@ +// Copyright © 2021 siddharth +// SPDX-License-Identifier: ISC + +package lib + +import "math/big" + +type DH struct { + p *big.Int + g *big.Int + pk *big.Int // Private key +} + +func NewDH(ps, gs string) (*DH, bool) { + p, ok := new(big.Int).SetString(StripSpaceChars(ps), 16) + if !ok { + return nil, false + } + g, ok := new(big.Int).SetString(StripSpaceChars(gs), 16) + if !ok { + return nil, false + } + + // Init DH. + dh := new(DH) + dh.p = p + dh.g = g + dh.pk = big.NewInt(RandomInt(1, 10000000)) + return dh, true +} + +// Return our public key. +func (dh *DH) Pub() *big.Int { + return new(big.Int).Exp(dh.g, dh.pk, dh.p) +} + +// Return shared secret between us and the other party. +// `pub` is the other party's public key. +func (dh *DH) SharedSecret(pub *big.Int) *big.Int { + return new(big.Int).Exp(pub, dh.pk, dh.p) +} diff --git a/lib/dh_test.go b/lib/dh_test.go new file mode 100644 index 0000000..f313d82 --- /dev/null +++ b/lib/dh_test.go @@ -0,0 +1,36 @@ +// Copyright © 2021 siddharth +// SPDX-License-Identifier: ISC + +package lib + +import "testing" + +func TestDH(t *testing.T) { + p := `ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024 +e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd +3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec +6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f +24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361 +c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552 +bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff +fffffffffffff` + g := "2" + + bobDH, ok := NewDH(p, g) + if !ok { + t.Errorf("Error: Unable to initialize Bob's DH\n") + return + } + + aliceDH, ok := NewDH(p, g) + if !ok { + t.Errorf("Error: Unable to initialize Alice's DH\n") + return + } + + bobSK := bobDH.SharedSecret(aliceDH.Pub()) + aliceSK := aliceDH.SharedSecret(bobDH.Pub()) + if bobSK.Cmp(aliceSK) != 0 { + t.Errorf("Error: Shared Secret for Bob and Alice is not the same\n") + } +} -- cgit v1.2.3