mirror of
https://github.com/billbuchanan/appliedcrypto.git
synced 2026-02-20 13:50:42 +00:00
113 lines
2.5 KiB
Go
113 lines
2.5 KiB
Go
package main
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import (
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"fmt"
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"flag"
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"gopkg.in/dedis/kyber.v2"
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"gopkg.in/dedis/kyber.v2/group/edwards25519"
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)
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var curve = edwards25519.NewBlakeSHA256Ed25519()
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var sha256 = curve.Hash()
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type Signature struct {
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r kyber.Point
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s kyber.Scalar
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}
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func Hash(s string) kyber.Scalar {
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sha256.Reset()
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sha256.Write([]byte(s))
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return curve.Scalar().SetBytes(sha256.Sum(nil))
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}
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// m: Message
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// x: Private key
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func Sign(m string, x kyber.Scalar) Signature {
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// Get the base of the curve.
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g := curve.Point().Base()
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// Pick a random k from allowed set.
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k := curve.Scalar().Pick(curve.RandomStream())
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// r = k * G (a.k.a the same operation as r = g^k)
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r := curve.Point().Mul(k, g)
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// Hash(m || r)
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e := Hash(m + r.String())
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// s = k - e * x
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s := curve.Scalar().Sub(k, curve.Scalar().Mul(e, x))
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return Signature{r: r, s: s}
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}
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// m: Message
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// S: Signature
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func PublicKey(m string, S Signature) kyber.Point {
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// Create a generator.
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g := curve.Point().Base()
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// e = Hash(m || r)
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e := Hash(m + S.r.String())
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// y = (r - s * G) * (1 / e)
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y := curve.Point().Sub(S.r, curve.Point().Mul(S.s, g))
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y = curve.Point().Mul(curve.Scalar().Div(curve.Scalar().One(), e), y)
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return y
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}
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// m: Message
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// s: Signature
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// y: Public key
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func Verify(m string, S Signature, y kyber.Point) bool {
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// Create a generator.
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g := curve.Point().Base()
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// e = Hash(m || r)
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e := Hash(m + S.r.String())
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// Attempt to reconstruct 's * G' with a provided signature; s * G = r - e * y
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sGv := curve.Point().Sub(S.r, curve.Point().Mul(e, y))
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// Construct the actual 's * G'
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sG := curve.Point().Mul(S.s, g)
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// Equality check; ensure signature and public key outputs to s * G.
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return sG.Equal(sGv)
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}
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func (S Signature) String() string {
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return fmt.Sprintf("(r=%s, s=%s)", S.r, S.s)
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}
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func main() {
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message := "abc"
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flag.Parse()
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args := flag.Args()
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message=args[0]
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privateKey := curve.Scalar().Pick(curve.RandomStream())
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publicKey := curve.Point().Mul(privateKey, curve.Point().Base())
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fmt.Printf("Message to sign: %s\n\n", message)
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fmt.Printf("Private key: %s\n", privateKey)
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fmt.Printf("Public key: %s\n\n", publicKey)
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signature := Sign(message, privateKey)
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fmt.Printf("Signature (r=%s, s=%s)\n\n", signature.r, signature.s)
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derivedPublicKey := PublicKey(message, signature)
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fmt.Printf("Derived public key: %s\n\n", derivedPublicKey)
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fmt.Printf("Checking keys %t\n", publicKey.Equal(derivedPublicKey))
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fmt.Printf("Checking signature %t\n\n", Verify(message, signature, publicKey))
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}
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