Add secp256k1 implementation with core components, context management, and testing suite

This commit introduces a complete Go implementation of the secp256k1 elliptic curve cryptographic primitives, including field and scalar arithmetic, group operations, context management for enhanced security, and a comprehensive testing suite. Key features include optimized scalar multiplication, context creation and destruction, and basic ECDSA operations. The README has been updated to reflect the new structure and usage examples.

p256k1/hash.go

@@ -2,6 +2,7 @@ package p256k1
 
 import (
 	"hash"
+
 	"github.com/minio/sha256-simd"
 )
 
@@ -26,7 +27,7 @@ func (h *SHA256) Initialize() {
 func (h *SHA256) InitializeTagged(tag []byte) {
 	// Compute SHA256(tag)
 	tagHash := sha256.Sum256(tag)
-	
+
 	// Initialize with SHA256(tag) || SHA256(tag)
 	h.hasher.Reset()
 	h.hasher.Write(tagHash[:])
@@ -43,7 +44,7 @@ func (h *SHA256) Finalize(output []byte) {
 	if len(output) != 32 {
 		panic("SHA-256 output must be 32 bytes")
 	}
-	
+
 	result := h.hasher.Sum(nil)
 	copy(output, result[:])
 }
@@ -58,16 +59,16 @@ func TaggedSHA256(output []byte, tag []byte, msg []byte) {
 	if len(output) != 32 {
 		panic("output must be 32 bytes")
 	}
-	
+
 	// Compute SHA256(tag)
 	tagHash := sha256.Sum256(tag)
-	
+
 	// Compute SHA256(SHA256(tag) || SHA256(tag) || msg)
 	hasher := sha256.New()
 	hasher.Write(tagHash[:])
 	hasher.Write(tagHash[:])
 	hasher.Write(msg)
-	
+
 	result := hasher.Sum(nil)
 	copy(output, result)
 }
@@ -77,7 +78,7 @@ func SHA256Simple(output []byte, input []byte) {
 	if len(output) != 32 {
 		panic("output must be 32 bytes")
 	}
-	
+
 	result := sha256.Sum256(input)
 	copy(output, result[:])
 }
@@ -100,24 +101,24 @@ func (h *HMACSHA256) Initialize(key []byte) {
 	for i := range h.v {
 		h.v[i] = 0x01
 	}
-	
+
 	// Initialize K = 0x00 0x00 0x00 ... 0x00
 	for i := range h.k {
 		h.k[i] = 0x00
 	}
-	
+
 	// K = HMAC_K(V || 0x00 || key)
 	h.updateK(0x00, key)
-	
+
 	// V = HMAC_K(V)
 	h.updateV()
-	
+
 	// K = HMAC_K(V || 0x01 || key)
 	h.updateK(0x01, key)
-	
+
 	// V = HMAC_K(V)
 	h.updateV()
-	
+
 	h.init = true
 }
 
@@ -145,14 +146,14 @@ func (h *HMACSHA256) Generate(output []byte) {
 	if !h.init {
 		panic("HMAC not initialized")
 	}
-	
+
 	outputLen := len(output)
 	generated := 0
-	
+
 	for generated < outputLen {
 		// V = HMAC_K(V)
 		h.updateV()
-		
+
 		// Copy V to output
 		toCopy := 32
 		if generated+toCopy > outputLen {
@@ -194,7 +195,7 @@ func NewHMACWithKey(key []byte) *HMAC {
 		outer:  NewSHA256(),
 		keyLen: len(key),
 	}
-	
+
 	// Prepare key
 	var k [64]byte
 	if len(key) > 64 {
@@ -206,22 +207,22 @@ func NewHMACWithKey(key []byte) *HMAC {
 	} else {
 		copy(k[:], key)
 	}
-	
+
 	// Create inner and outer keys
 	var ikey, okey [64]byte
 	for i := 0; i < 64; i++ {
 		ikey[i] = k[i] ^ 0x36
 		okey[i] = k[i] ^ 0x5c
 	}
-	
+
 	// Initialize inner hash with inner key
 	h.inner.Initialize()
 	h.inner.Write(ikey[:])
-	
+
 	// Initialize outer hash with outer key
 	h.outer.Initialize()
 	h.outer.Write(okey[:])
-	
+
 	return h
 }
 
@@ -235,11 +236,11 @@ func (h *HMAC) Finalize(output []byte) {
 	if len(output) != 32 {
 		panic("HMAC output must be 32 bytes")
 	}
-	
+
 	// Get inner hash result
 	var innerResult [32]byte
 	h.inner.Finalize(innerResult[:])
-	
+
 	// Complete outer hash
 	h.outer.Write(innerResult[:])
 	h.outer.Finalize(output)