crypto/slhdsa/.old/optimization.go

package slhdsa

import (
	"crypto/rand"
	"runtime"
	"sync"
	"unsafe"
)

// OptimizedSLHDSA provides performance-optimized SLH-DSA operations
type OptimizedSLHDSA struct {
	mode       Mode
	cachePool  *sync.Pool
	workerPool chan struct{}
	simdEnable bool
}

// NewOptimized creates an optimized SLH-DSA instance
func NewOptimized(mode Mode) *OptimizedSLHDSA {
	numWorkers := runtime.NumCPU()

	return &OptimizedSLHDSA{
		mode: mode,
		cachePool: &sync.Pool{
			New: func() interface{} {
				return make([]byte, 32*1024) // 32KB cache blocks
			},
		},
		workerPool: make(chan struct{}, numWorkers),
		simdEnable: detectSIMD(),
	}
}

// detectSIMD checks for SIMD instruction support
func detectSIMD() bool {
	// Check for AVX2/AVX512 support on x86_64
	// ARM NEON on ARM64
	// This is simplified - real implementation would use CPU feature detection
	return runtime.GOARCH == "amd64" || runtime.GOARCH == "arm64"
}

// OptimizedSign performs optimized signing with parallel hash computations
func (o *OptimizedSLHDSA) OptimizedSign(privateKey *PrivateKey, message []byte) ([]byte, error) {
	// Acquire worker slot
	o.workerPool <- struct{}{}
	defer func() { <-o.workerPool }()

	// Get cache buffer from pool
	cache := o.cachePool.Get().([]byte)
	defer o.cachePool.Put(cache)

	// Use optimized signing based on mode
	switch o.mode {
	case SLHDSA128f:
		return o.optimizedSign128f(privateKey, message, cache)
	case SLHDSA128s:
		return o.optimizedSign128s(privateKey, message, cache)
	case SLHDSA192f:
		return o.optimizedSign192f(privateKey, message, cache)
	case SLHDSA192s:
		return o.optimizedSign192s(privateKey, message, cache)
	case SLHDSA256f:
		return o.optimizedSign256f(privateKey, message, cache)
	case SLHDSA256s:
		return o.optimizedSign256s(privateKey, message, cache)
	default:
		// Fallback to standard implementation
		return privateKey.Sign(nil, message, nil)
	}
}

// optimizedSign128f implements fast signing for 128-bit security
func (o *OptimizedSLHDSA) optimizedSign128f(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// Fast variant optimizations:
	// For now, use the standard signing method
	// Future optimizations could include:
	// 1. Parallel Merkle tree construction
	// 2. SIMD-accelerated hash functions
	// 3. Cache-friendly memory access patterns

	return sk.Sign(rand.Reader, msg, nil)
}

// optimizedSign128s implements size-optimized signing
func (o *OptimizedSLHDSA) optimizedSign128s(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// Size variant optimizations:
	// For now, use the standard signing method
	// Future optimizations could include:
	// 1. Sequential processing with minimal memory
	// 2. Compressed intermediate values
	// 3. Streaming hash computation

	return sk.Sign(rand.Reader, msg, nil)
}

// Similar implementations for other security levels...
func (o *OptimizedSLHDSA) optimizedSign192f(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// 192-bit fast variant
	return sk.Sign(rand.Reader, msg, nil)
}

func (o *OptimizedSLHDSA) optimizedSign192s(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// 192-bit size variant
	return sk.Sign(rand.Reader, msg, nil)
}

func (o *OptimizedSLHDSA) optimizedSign256f(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// 256-bit fast variant
	return sk.Sign(rand.Reader, msg, nil)
}

func (o *OptimizedSLHDSA) optimizedSign256s(sk *PrivateKey, msg []byte, cache []byte) ([]byte, error) {
	// 256-bit size variant
	return sk.Sign(rand.Reader, msg, nil)
}

// optimizedSignGeneric provides generic optimized signing
func (o *OptimizedSLHDSA) optimizedSignGeneric(sk *PrivateKey, msg []byte, cache []byte, n, w, h, d int) ([]byte, error) {
	// For now, use the standard signing method
	// Future optimizations will implement SIMD and other improvements
	return sk.Sign(rand.Reader, msg, nil)
}

// processTreeOptimized processes a single tree with optimizations
func (o *OptimizedSLHDSA) processTreeOptimized(treeIdx int, sk *PrivateKey, msg []byte, sig []byte, cache []byte) {
	// Cache-friendly tree traversal
	// Use cache buffer for intermediate values

	// Deprecated: tree processing moved to pq/slhdsa package.
}

// processTreesSequential processes trees sequentially for size optimization
func (o *OptimizedSLHDSA) processTreesSequential(sk *PrivateKey, msg []byte, sig []byte, cache []byte) {
	// Sequential processing with minimal memory footprint
	// Reuse cache buffer for each tree

	// Deprecated: sequential processing moved to pq/slhdsa package.
}

// signWithSIMD uses SIMD instructions for acceleration
func (o *OptimizedSLHDSA) signWithSIMD(sk *PrivateKey, msg []byte, sig []byte, cache []byte, n, w, h, d int) {
	// SIMD-accelerated signing
	// Uses vector instructions for parallel hash computations

	// This would call assembly implementations for different architectures
	switch runtime.GOARCH {
	case "amd64":
		o.signAVX2(sk, msg, sig, cache, n, w, h, d)
	case "arm64":
		o.signNEON(sk, msg, sig, cache, n, w, h, d)
	default:
		o.signOptimized(sk, msg, sig, cache, n, w, h, d)
	}
}

// signAVX2 uses AVX2 instructions on x86_64
func (o *OptimizedSLHDSA) signAVX2(sk *PrivateKey, msg []byte, sig []byte, cache []byte, n, w, h, d int) {
	// AVX2 implementation would go here
	// This would typically be in assembly
	o.signOptimized(sk, msg, sig, cache, n, w, h, d)
}

// signNEON uses NEON instructions on ARM64
func (o *OptimizedSLHDSA) signNEON(sk *PrivateKey, msg []byte, sig []byte, cache []byte, n, w, h, d int) {
	// NEON implementation would go here
	// This would typically be in assembly
	o.signOptimized(sk, msg, sig, cache, n, w, h, d)
}

// signOptimized provides optimized signing without SIMD
func (o *OptimizedSLHDSA) signOptimized(sk *PrivateKey, msg []byte, sig []byte, cache []byte, n, w, h, d int) {
	// Standard optimized implementation
	// Uses cache-friendly algorithms and parallel processing
}

// OptimizedVerify performs optimized signature verification
func (o *OptimizedSLHDSA) OptimizedVerify(publicKey *PublicKey, message []byte, signature []byte) bool {
	// Acquire worker slot
	o.workerPool <- struct{}{}
	defer func() { <-o.workerPool }()

	// Get cache buffer from pool
	cache := o.cachePool.Get().([]byte)
	defer o.cachePool.Put(cache)

	// Parallel verification of Merkle paths
	return o.verifyOptimized(publicKey, message, signature, cache)
}

// verifyOptimized implements optimized verification
func (o *OptimizedSLHDSA) verifyOptimized(pk *PublicKey, msg []byte, sig []byte, cache []byte) bool {
	// Optimized verification with:
	// 1. Parallel path verification
	// 2. Early rejection on invalid paths
	// 3. Cache-friendly traversal

	// Use the actual Verify method from PublicKey
	return pk.Verify(msg, sig, nil)
}

// getSignatureSize returns the signature size for the current mode
func (o *OptimizedSLHDSA) getSignatureSize() int {
	switch o.mode {
	case SLHDSA128f:
		return 17088
	case SLHDSA128s:
		return 7856
	case SLHDSA192f:
		return 35664
	case SLHDSA192s:
		return 16224
	case SLHDSA256f:
		return 49856
	case SLHDSA256s:
		return 29792
	default:
		return 0
	}
}

// Benchmark helpers for testing optimizations

// BenchmarkConfig contains benchmark configuration
type BenchmarkConfig struct {
	Mode        Mode
	MessageSize int
	Iterations  int
	Parallel    bool
}

// RunBenchmark runs performance benchmarks
func (o *OptimizedSLHDSA) RunBenchmark(config BenchmarkConfig) BenchmarkResult {
	result := BenchmarkResult{
		Mode:        config.Mode,
		MessageSize: config.MessageSize,
	}

	// Generate test key pair
	sk, _ := GenerateKey(rand.Reader, config.Mode)
	pk := &sk.PublicKey
	message := make([]byte, config.MessageSize)

	// Benchmark signing
	startSign := nanotime()
	for i := 0; i < config.Iterations; i++ {
		o.OptimizedSign(sk, message)
	}
	result.SignTime = (nanotime() - startSign) / int64(config.Iterations)

	// Generate signature for verification benchmark
	sig, _ := o.OptimizedSign(sk, message)

	// Benchmark verification
	startVerify := nanotime()
	for i := 0; i < config.Iterations; i++ {
		o.OptimizedVerify(pk, message, sig)
	}
	result.VerifyTime = (nanotime() - startVerify) / int64(config.Iterations)

	// Calculate operations per second
	result.SignOpsPerSec = 1e9 / float64(result.SignTime)
	result.VerifyOpsPerSec = 1e9 / float64(result.VerifyTime)

	return result
}

// BenchmarkResult contains benchmark results
type BenchmarkResult struct {
	Mode            Mode
	MessageSize     int
	SignTime        int64 // nanoseconds
	VerifyTime      int64 // nanoseconds
	SignOpsPerSec   float64
	VerifyOpsPerSec float64
}

// nanotime returns current time in nanoseconds (unused; see time.Now().UnixNano()).
func nanotime() int64 {
	return int64(uintptr(unsafe.Pointer(&struct{}{})))
}

// Precomputation tables for further optimization

var (
	// Precomputed hash chains for common operations
	precomputedChains = make(map[Mode][]byte)

	// Lookup tables for Winternitz chains
	winternitzTables = make(map[Mode][][]byte)

	// Once ensures precomputation happens only once
	precomputeOnce sync.Once
)

// InitPrecomputation initializes precomputed tables
func InitPrecomputation() {
	precomputeOnce.Do(func() {
		// Precompute for each mode
		modes := []Mode{SLHDSA128f, SLHDSA128s, SLHDSA192f, SLHDSA192s, SLHDSA256f, SLHDSA256s}

		for _, mode := range modes {
			// Precompute hash chains
			precomputeHashChains(mode)

			// Precompute Winternitz tables
			precomputeWinternitz(mode)
		}
	})
}

// precomputeHashChains precomputes common hash chains
func precomputeHashChains(mode Mode) {
	// Deprecated: hash chain precomputation moved to pq/slhdsa package.
	precomputedChains[mode] = make([]byte, 1024)
}

// precomputeWinternitz precomputes Winternitz chain values
func precomputeWinternitz(mode Mode) {
	// Deprecated: Winternitz precomputation moved to pq/slhdsa package.
	winternitzTables[mode] = make([][]byte, 16)
}