optimize quintic extension & signing/validating signatures

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.22.x', '1.23.x', '1.24.x']
+        go-version: ['1.23.x', '1.24.x']
     steps:
       - uses: actions/checkout@v4
         with:
@@ -33,3 +33,25 @@ jobs:
       - name: Run fuzzy field tests
         run: |
           go test -tags=fuzz -fuzz=Fuzz -fuzztime=30s github.com/elliottech/poseidon_crypto/field
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Setup Go 1.23.x
+        uses: actions/setup-go@v5
+        with:
+          go-version: 1.23.x
+
+      # TODO: update version
+      - name: Install golangci-lint
+        run: |
+          go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.61.0
+
+      - name: Run golangci-lint
+        run: |
+          golangci-lint run ./...

.golangci.yaml

@@ -0,0 +1,35 @@
+run:
+  # The default concurrency value is the number of available CPU.
+  concurrency: 4
+  timeout: 5m
+
+linters:
+  enable:
+    - unparam
+    - bidichk
+    - durationcheck
+    - gocritic
+    - gosec
+    - unconvert
+    - exhaustruct
+
+linters-settings:
+  govet:
+    enable:
+      - nilness
+    disable:
+      - composites
+  gocritic:
+    disabled-checks:
+      - captLocal
+      - ifElseChain
+
+issues:
+  max-issues-per-linter: 100
+  max-same-issues: 100
+
+  exclude-rules:
+    - path: ".*_test.go"
+      linters:
+        - gosec
+      text: "G115"

curve/ecgfp5/affine_point.go

@@ -32,18 +32,18 @@ func (p *AffinePoint) SetNeg() {
 // i*P for i = 1 to n (win[0] contains P, win[1] contains 2*P, and
 // so on). Index value k is an integer in the -n to n range; returned
 // point is k*P.
-func (p *AffinePoint) SetLookup(win []AffinePoint, k int32) {
+func Lookup(win []AffinePoint, k int32) AffinePoint {
 	// sign = 0xFFFFFFFF if k < 0, 0x00000000 otherwise
-	sign := uint32(k >> 31)
+	sign := uint32(k >> 31) //nolint:gosec
 	// ka = abs(k)
-	ka := (uint32(k) ^ sign) - sign
+	ka := (uint32(k) ^ sign) - sign //nolint:gosec
 	// km1 = ka - 1
 	km1 := ka - 1
 
 	x := gFp5.FP5_ZERO
 	u := gFp5.FP5_ZERO
 	for i := 0; i < len(win); i++ {
-		m := km1 - uint32(i)
+		m := km1 - uint32(i) //nolint:gosec
 		c_1 := (m | (^m + 1)) >> 31
 		c := uint64(c_1) - 1
 		if c != 0 {
@@ -55,18 +55,12 @@ func (p *AffinePoint) SetLookup(win []AffinePoint, k int32) {
 
 	// If k < 0, then we must negate the point.
 	c := uint64(sign) | (uint64(sign) << 32)
-	p.x = x
-	p.u = u
 
 	if c != 0 {
-		p.u = gFp5.Neg(p.u)
+		u = gFp5.Neg(u)
 	}
-}
 
-func Lookup(win []AffinePoint, k int32) AffinePoint {
-	r := AFFINE_NEUTRAL
-	r.SetLookup(win, k)
-	return r
+	return AffinePoint{x, u}
 }
 
 // Same as lookup(), except this implementation is variable-time.