crypto/slhdsa/slhdsa_placeholder.go.bak

// Copyright (C) 2025, Lux Industries Inc. All rights reserved.
// Package slhdsa provides SLH-DSA (FIPS 205) stateless hash-based signatures
// This is a placeholder implementation for CI testing

package slhdsa

import (
	"crypto"
	"crypto/sha256"
	"errors"
	"io"
)

// Security parameters for SLH-DSA (Stateless Hash-Based Digital Signature Algorithm)
const (
	// SLH-DSA-SHA2-128s (Small signatures, Level 1 security)
	SLHDSA128sPublicKeySize  = 32   // bytes
	SLHDSA128sPrivateKeySize = 64   // bytes
	SLHDSA128sSignatureSize  = 7856 // bytes

	// SLH-DSA-SHA2-128f (Fast signing, Level 1 security)
	SLHDSA128fPublicKeySize  = 32    // bytes
	SLHDSA128fPrivateKeySize = 64    // bytes
	SLHDSA128fSignatureSize  = 17088 // bytes

	// SLH-DSA-SHA2-192s (Small signatures, Level 3 security)
	SLHDSA192sPublicKeySize  = 48    // bytes
	SLHDSA192sPrivateKeySize = 96    // bytes
	SLHDSA192sSignatureSize  = 16224 // bytes

	// SLH-DSA-SHA2-192f (Fast signing, Level 3 security)
	SLHDSA192fPublicKeySize  = 48    // bytes
	SLHDSA192fPrivateKeySize = 96    // bytes
	SLHDSA192fSignatureSize  = 35664 // bytes

	// SLH-DSA-SHA2-256s (Small signatures, Level 5 security)
	SLHDSA256sPublicKeySize  = 64    // bytes
	SLHDSA256sPrivateKeySize = 128   // bytes
	SLHDSA256sSignatureSize  = 29792 // bytes

	// SLH-DSA-SHA2-256f (Fast signing, Level 5 security)
	SLHDSA256fPublicKeySize  = 64    // bytes
	SLHDSA256fPrivateKeySize = 128   // bytes
	SLHDSA256fSignatureSize  = 49856 // bytes
)

// Mode represents the SLH-DSA parameter set
type Mode int

const (
	SLHDSA128s Mode = iota + 1
	SLHDSA128f
	SLHDSA192s
	SLHDSA192f
	SLHDSA256s
	SLHDSA256f
)

// PublicKey represents an SLH-DSA public key
type PublicKey struct {
	mode Mode
	data []byte
}

// PrivateKey represents an SLH-DSA private key
type PrivateKey struct {
	PublicKey
	data []byte
}

// GenerateKey generates a new SLH-DSA key pair
func GenerateKey(rand io.Reader, mode Mode) (*PrivateKey, error) {
	var pubKeySize, privKeySize int

	switch mode {
	case SLHDSA128s:
		pubKeySize = SLHDSA128sPublicKeySize
		privKeySize = SLHDSA128sPrivateKeySize
	case SLHDSA128f:
		pubKeySize = SLHDSA128fPublicKeySize
		privKeySize = SLHDSA128fPrivateKeySize
	case SLHDSA192s:
		pubKeySize = SLHDSA192sPublicKeySize
		privKeySize = SLHDSA192sPrivateKeySize
	case SLHDSA192f:
		pubKeySize = SLHDSA192fPublicKeySize
		privKeySize = SLHDSA192fPrivateKeySize
	case SLHDSA256s:
		pubKeySize = SLHDSA256sPublicKeySize
		privKeySize = SLHDSA256sPrivateKeySize
	case SLHDSA256f:
		pubKeySize = SLHDSA256fPublicKeySize
		privKeySize = SLHDSA256fPrivateKeySize
	default:
		return nil, errors.New("invalid SLH-DSA mode")
	}

	// Check for nil random source
	if rand == nil {
		return nil, errors.New("random source is nil")
	}

	// Placeholder implementation - generate random keys
	// In real SLH-DSA, public key is derived from private key
	privBytes := make([]byte, privKeySize)
	if _, err := io.ReadFull(rand, privBytes); err != nil {
		return nil, err
	}
	
	// Derive public key from private key for consistency
	h := sha256.New()
	h.Write(privBytes[:32]) // Use first part as seed
	h.Write([]byte("slhdsa-public"))
	pubSeed := h.Sum(nil)
	
	pubBytes := make([]byte, pubKeySize)
	// Fill public key with deterministic data
	for i := 0; i < pubKeySize; i += 32 {
		h.Reset()
		h.Write(pubSeed)
		h.Write([]byte{byte(i / 32)})
		hash := h.Sum(nil)
		end := i + 32
		if end > pubKeySize {
			end = pubKeySize
		}
		copy(pubBytes[i:end], hash)
	}

	return &PrivateKey{
		PublicKey: PublicKey{
			mode: mode,
			data: pubBytes,
		},
		data: privBytes,
	}, nil
}

// Sign signs a message using the private key
func (priv *PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) ([]byte, error) {
	if priv == nil {
		return nil, errors.New("private key is nil")
	}
	
	var sigSize int

	switch priv.PublicKey.mode {
	case SLHDSA128s:
		sigSize = SLHDSA128sSignatureSize
	case SLHDSA128f:
		sigSize = SLHDSA128fSignatureSize
	case SLHDSA192s:
		sigSize = SLHDSA192sSignatureSize
	case SLHDSA192f:
		sigSize = SLHDSA192fSignatureSize
	case SLHDSA256s:
		sigSize = SLHDSA256sSignatureSize
	case SLHDSA256f:
		sigSize = SLHDSA256fSignatureSize
	default:
		return nil, errors.New("invalid SLH-DSA mode")
	}

	// Placeholder: create deterministic signature that can be verified
	// Start with hash of public key and message (what Verify expects)
	h := sha256.New()
	h.Write(priv.PublicKey.data)
	h.Write(message)
	hash := h.Sum(nil)

	signature := make([]byte, sigSize)
	// Copy the hash to beginning of signature
	copy(signature[:32], hash)

	// Fill rest with deterministic data based on private key
	// SLH-DSA is stateless so signature should be deterministic
	h.Reset()
	h.Write(priv.data)
	h.Write(message)
	privHash := h.Sum(nil)

	for i := 32; i < sigSize; i += len(privHash) {
		end := i + len(privHash)
		if end > sigSize {
			end = sigSize
		}
		copy(signature[i:end], privHash)
		h.Write(privHash) // Generate more data
		privHash = h.Sum(nil)
	}

	return signature, nil
}

// Verify verifies a signature using the public key
func (pub *PublicKey) Verify(message, signature []byte, opts crypto.SignerOpts) bool {
	if pub == nil {
		return false
	}
	
	var expectedSigSize int

	switch pub.mode {
	case SLHDSA128s:
		expectedSigSize = SLHDSA128sSignatureSize
	case SLHDSA128f:
		expectedSigSize = SLHDSA128fSignatureSize
	case SLHDSA192s:
		expectedSigSize = SLHDSA192sSignatureSize
	case SLHDSA192f:
		expectedSigSize = SLHDSA192fSignatureSize
	case SLHDSA256s:
		expectedSigSize = SLHDSA256sSignatureSize
	case SLHDSA256f:
		expectedSigSize = SLHDSA256fSignatureSize
	default:
		return false
	}

	// Check signature size
	if len(signature) != expectedSigSize {
		return false
	}

	// Placeholder verification for SLH-DSA
	// Recompute expected signature start based on public key and message
	h := sha256.New()
	h.Write(pub.data)
	h.Write(message)
	expectedSigStart := h.Sum(nil)

	// Check if first 32 bytes match
	if len(signature) < 32 {
		return false
	}

	// Compare first 32 bytes
	for i := 0; i < 32; i++ {
		if signature[i] != expectedSigStart[i] {
			return false
		}
	}

	return true
}

// Bytes returns the public key as bytes
func (pub *PublicKey) Bytes() []byte {
	return pub.data
}

// Bytes returns the private key as bytes
func (priv *PrivateKey) Bytes() []byte {
	return priv.data
}

// PublicKeyFromBytes reconstructs a public key from bytes
func PublicKeyFromBytes(data []byte, mode Mode) (*PublicKey, error) {
	var expectedSize int

	switch mode {
	case SLHDSA128s, SLHDSA128f:
		expectedSize = SLHDSA128sPublicKeySize
	case SLHDSA192s, SLHDSA192f:
		expectedSize = SLHDSA192sPublicKeySize
	case SLHDSA256s, SLHDSA256f:
		expectedSize = SLHDSA256sPublicKeySize
	default:
		return nil, errors.New("invalid SLH-DSA mode")
	}

	if len(data) != expectedSize {
		return nil, errors.New("invalid public key size")
	}

	return &PublicKey{
		mode: mode,
		data: data,
	}, nil
}

// PrivateKeyFromBytes reconstructs a private key from bytes
func PrivateKeyFromBytes(data []byte, mode Mode) (*PrivateKey, error) {
	var expectedSize int
	var pubKeySize int

	switch mode {
	case SLHDSA128s, SLHDSA128f:
		expectedSize = SLHDSA128sPrivateKeySize
		pubKeySize = SLHDSA128sPublicKeySize
	case SLHDSA192s, SLHDSA192f:
		expectedSize = SLHDSA192sPrivateKeySize
		pubKeySize = SLHDSA192sPublicKeySize
	case SLHDSA256s, SLHDSA256f:
		expectedSize = SLHDSA256sPrivateKeySize
		pubKeySize = SLHDSA256sPublicKeySize
	default:
		return nil, errors.New("invalid SLH-DSA mode")
	}

	if len(data) != expectedSize {
		return nil, errors.New("invalid private key size")
	}

	// Derive public key from private key (same as GenerateKey)
	h := sha256.New()
	h.Write(data[:32]) // Use first part as seed
	h.Write([]byte("slhdsa-public"))
	pubSeed := h.Sum(nil)
	
	pubData := make([]byte, pubKeySize)
	// Fill public key with deterministic data
	for i := 0; i < pubKeySize; i += 32 {
		h.Reset()
		h.Write(pubSeed)
		h.Write([]byte{byte(i / 32)})
		hash := h.Sum(nil)
		end := i + 32
		if end > pubKeySize {
			end = pubKeySize
		}
		copy(pubData[i:end], hash)
	}

	return &PrivateKey{
		PublicKey: PublicKey{
			mode: mode,
			data: pubData,
		},
		data: data,
	}, nil
}