Add GHA (tests & lint), add descr, update readme

.github/workflows/lint.yml

@@ -0,0 +1,16 @@
+name: Lint
+on: [ push, pull_request ]
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v1
+        with:
+          go-version: 1.14.x
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Lint
+        run: |
+          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.30.0
+          $(go env GOPATH)/bin/golangci-lint run --timeout=5m -c .golangci.yml

.github/workflows/test.yml

@@ -0,0 +1,19 @@
+name: Test
+on: [push, pull_request]
+jobs:
+  test:
+    # matrix strategy from: https://github.com/mvdan/github-actions-golang/blob/master/.github/workflows/test.yml
+    strategy:
+      matrix:
+        go-version: [1.13.x, 1.14.x]
+        platform: [ubuntu-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: Run tests
+      run: go test ./...

.golangci.yml

@@ -0,0 +1,17 @@
+issues:
+        max-same-issues: 0
+        exclude-use-default: false
+linters:
+        enable:
+        - whitespace
+        - gosec
+        - gci
+        - misspell
+        - gomnd
+        - gofmt
+        - goimports
+        - lll
+        - golint
+linters-settings:
+        lll:
+                line-length: 100

README.md

@@ -1,5 +1,6 @@
-# go-blindsecp256k1
-Blind signature over [secp256k1](https://en.bitcoin.it/wiki/Secp256k1), based on *"[An Efficient Blind Signature Scheme Based on the Elliptic CurveDiscrete Logarithm Problem](http://www.isecure-journal.com/article_39171_47f9ec605dd3918c2793565ec21fcd7a.pdf)"* paper.
+# go-blindsecp256k1 [![GoDoc](https://godoc.org/github.com/arnaucube/go-blindsecp256k1?status.svg)](https://godoc.org/github.com/arnaucube/go-blindsecp256k1) [![Go Report Card](https://goreportcard.com/badge/github.com/arnaucube/go-blindsecp256k1)](https://goreportcard.com/report/github.com/arnaucube/go-blindsecp256k1) [![Test](https://github.com/arnaucube/go-blindsecp256k1/workflows/Test/badge.svg)](https://github.com/arnaucube/go-blindsecp256k1/actions?query=workflow%3ATest)
+
+Blind signature over [secp256k1](https://en.bitcoin.it/wiki/Secp256k1), based on *"[An Efficient Blind Signature Scheme Based on the Elliptic Curve Discrete Logarithm Problem](http://www.isecure-journal.com/article_39171_47f9ec605dd3918c2793565ec21fcd7a.pdf)"* paper.
 
 **WARNING**: this repo is experimental, do not use in production.
 

blindsecp256k1.go

@@ -2,6 +2,7 @@
 // http://www.isecure-journal.com/article_39171_47f9ec605dd3918c2793565ec21fcd7a.pdf
 //
 // LICENSE can be found at https://github.com/arnaucube/go-blindsecp256k1/blob/master/LICENSE
+//
 package blindsecp256k1
 
 // WARNING: WIP code
@@ -14,20 +15,24 @@ import (
 	"github.com/ethereum/go-ethereum/crypto/secp256k1"
 )
 
-type Point struct {
-	X *big.Int
-	Y *big.Int
-}
-
 var (
+	// G represents the base point of secp256k1
 	G *Point = &Point{
 		X: secp256k1.S256().Gx,
 		Y: secp256k1.S256().Gy,
 	}
 
+	// N represents the order of G of secp256k1
 	N *big.Int = secp256k1.S256().N
 )
 
+// Point represents a point on the secp256k1 curve
+type Point struct {
+	X *big.Int
+	Y *big.Int
+}
+
+// Add performs the Point addition
 func (p *Point) Add(q *Point) *Point {
 	x, y := secp256k1.S256().Add(p.X, p.Y, q.X, q.Y)
 	return &Point{
@@ -36,6 +41,7 @@ func (p *Point) Add(q *Point) *Point {
 	}
 }
 
+// Mul performs the Point scalar multiplication
 func (p *Point) Mul(scalar *big.Int) *Point {
 	x, y := secp256k1.S256().ScalarMult(p.X, p.Y, scalar.Bytes())
 	return &Point{
@@ -44,6 +50,7 @@ func (p *Point) Mul(scalar *big.Int) *Point {
 	}
 }
 
+// WIP
 func newRand() *big.Int {
 	var b [32]byte
 	_, err := rand.Read(b[:])
@@ -54,108 +61,129 @@ func newRand() *big.Int {
 	return new(big.Int).Mod(bi, N)
 }
 
+// PrivateKey represents the signer's private key
 type PrivateKey big.Int
+
+// PublicKey represents the signer's public key
 type PublicKey Point
 
+// NewPrivateKey returns a new random private key
 func NewPrivateKey() *PrivateKey {
 	k := newRand()
 	sk := PrivateKey(*k)
 	return &sk
 }
 
+// BigInt returns a *big.Int representation of the PrivateKey
 func (sk *PrivateKey) BigInt() *big.Int {
 	return (*big.Int)(sk)
 }
 
+// Public returns the PublicKey from the PrivateKey
 func (sk *PrivateKey) Public() *PublicKey {
 	Q := G.Mul(sk.BigInt())
 	pk := PublicKey(*Q)
 	return &pk
 }
 
+// Point returns a *Point representation of the PublicKey
 func (pk *PublicKey) Point() *Point {
 	return (*Point)(pk)
 }
 
+// SignerPrivateData contains the secret values from the Signer
 type SignerPrivateData struct {
-	d *PrivateKey
-	k *big.Int
+	D *PrivateKey
+	K *big.Int
 }
+
+// SignerPublicData contains the public values from the Signer (generated from
+// its SignerPrivateData)
 type SignerPublicData struct {
 	// Q is the Signer Public Key
 	Q *PublicKey // = skG
 	R *Point     // = kG
 }
 
+// NewSigner returns a new SignerPrivateData with random D & K
 func NewSigner() *SignerPrivateData {
 	sk := NewPrivateKey()
 	k := newRand()
 	return &SignerPrivateData{
-		d: sk,
-		k: k,
+		D: sk,
+		K: k,
 	}
 }
 
+// PublicData returns the SignerPublicData from the SignerPrivateData
 func (signer *SignerPrivateData) PublicData() *SignerPublicData {
 	return &SignerPublicData{
-		Q: signer.d.Public(), // Q = dG
-		R: G.Mul(signer.k),   // R = kG
+		Q: signer.D.Public(), // Q = dG
+		R: G.Mul(signer.K),   // R = kG
 	}
 }
 
+// BlindSign performs the blind signature on the given mBlinded using
+// SignerPrivateData values
 func (signer *SignerPrivateData) BlindSign(mBlinded *big.Int) *big.Int {
 	// TODO add pending checks
 	// s' = d(m') + k
 	sBlind := new(big.Int).Add(
-		new(big.Int).Mul(signer.d.BigInt(), mBlinded),
-		signer.k)
+		new(big.Int).Mul(signer.D.BigInt(), mBlinded),
+		signer.K)
 	return sBlind
 }
 
+// UserSecretData contains the secret values from the User (a, b, c) and the
+// public F
 type UserSecretData struct {
-	a *big.Int
-	b *big.Int
-	c *big.Int
+	A *big.Int
+	B *big.Int
+	C *big.Int
 
 	F *Point // public
 }
 
+// Blind performs the blinding operation on m using SignerPublicData parameters
 func Blind(m *big.Int, signer *SignerPublicData) (*big.Int, *UserSecretData) {
 	u := &UserSecretData{}
-	u.a = newRand()
-	u.b = newRand()
-	u.c = newRand()
-	binv := new(big.Int).ModInverse(u.b, N)
+	u.A = newRand()
+	u.B = newRand()
+	u.C = newRand()
+	binv := new(big.Int).ModInverse(u.B, N)
 
 	// F = b^-1 R + a b^-1 Q + c G
 	bR := signer.R.Mul(binv)
-	abinv := new(big.Int).Mul(u.a, binv)
+	abinv := new(big.Int).Mul(u.A, binv)
 	abinv = new(big.Int).Mod(abinv, N)
 	abQ := signer.Q.Point().Mul(abinv)
-	cG := G.Mul(u.c)
+	cG := G.Mul(u.C)
 	u.F = bR.Add(abQ).Add(cG)
 	// TODO check F==O
 
 	r := new(big.Int).Mod(u.F.X, N)
 
 	// m' = br(m)+a
-	br := new(big.Int).Mul(u.b, r)
+	br := new(big.Int).Mul(u.B, r)
 	brm := new(big.Int).Mul(br, m)
-	mBlinded := new(big.Int).Add(brm, u.a)
+	mBlinded := new(big.Int).Add(brm, u.A)
 	mBlinded = new(big.Int).Mod(mBlinded, N)
 	return mBlinded, u
 }
 
+// Signature contains the signature values S & F
 type Signature struct {
 	S *big.Int
 	F *Point
 }
 
+// Unblind performs the unblinding operation of the blinded signature for the
+// given message m and the UserSecretData
 func Unblind(sBlind, m *big.Int, u *UserSecretData) *Signature {
 	// s = b^-1 s' + c
-	binv := new(big.Int).ModInverse(u.b, N)
+	binv := new(big.Int).ModInverse(u.B, N)
 	bs := new(big.Int).Mul(binv, sBlind)
-	s := new(big.Int).Add(bs, u.c)
+	s := new(big.Int).Add(bs, u.C)
 	s = new(big.Int).Mod(s, N)
 
 	return &Signature{
@@ -164,6 +192,7 @@ func Unblind(sBlind, m *big.Int, u *UserSecretData) *Signature {
 	}
 }
 
+// Verify checks the signature of the message m for the given PublicKey
 func Verify(m *big.Int, signature *Signature, q *PublicKey) bool {
 	// TODO add pending checks
 	sG := G.Mul(signature.S) // sG