From a83f507ed8a6032e1587e5cbf3277e1905439e06 Mon Sep 17 00:00:00 2001
From: ston1th <ston1th@giftfish.de>
Date: Sun, 12 Jul 2020 17:04:07 +0200
Subject: [PATCH] added dsa secret channel

---
 dsa.go | 36 ++++++++++++++++++++++++++++++++++++
 go.mod |  2 ++
 2 files changed, 38 insertions(+)
 create mode 100644 dsa.go

diff --git a/dsa.go b/dsa.go
new file mode 100644
index 0000000..e264b2e
--- /dev/null
+++ b/dsa.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"bytes"
+	"crypto/dsa"
+	"crypto/rand"
+	"fmt"
+	"math/big"
+)
+
+func extract(priv *dsa.PrivateKey, r, s *big.Int, hash []byte) string {
+	z := new(big.Int).SetBytes(hash)
+	h := new(big.Int).Mod(z, priv.Parameters.Q)
+	ns := new(big.Int).ModInverse(s, priv.Parameters.Q)
+	xr := new(big.Int).Mul(priv.X, r)
+	k := new(big.Int).Add(h, xr)
+	num := new(big.Int).Mul(ns, k)
+	msg := new(big.Int).Mod(num, priv.Parameters.Q)
+	return string(msg.Bytes())
+}
+
+func main() {
+	priv := new(dsa.PrivateKey)
+	err := dsa.GenerateParameters(&priv.Parameters, rand.Reader, dsa.L1024N160)
+	fmt.Println(err)
+	err = dsa.GenerateKey(priv, rand.Reader)
+	fmt.Println(err)
+	hash := []byte("hello")
+	msg := []byte("0000000000000000world")
+	buf := bytes.NewBuffer(msg)
+	r, s, err := dsa.Sign(buf, priv, hash)
+	fmt.Println(r, s, err)
+	fmt.Println(dsa.Verify(&priv.PublicKey, hash, r, s))
+	msg1 := extract(priv, r, s, hash)
+	fmt.Println(msg1)
+}
diff --git a/go.mod b/go.mod
index 6bd0de5..c413313 100644
--- a/go.mod
+++ b/go.mod
@@ -1 +1,3 @@
 module main
+
+go 1.14