Rename project

docs/IMPLEMENTATION.md

@@ -3,32 +3,32 @@
 ## Phase 1: Proof of Work Package Implementation
 **Goal**: Create standalone, testable PoW package with HMAC-signed stateless challenges
 
-- [ ] **Project Setup**
+- [X] **Project Setup**
-  - [ ] Initialize Go module and basic project structure
+  - [X] Initialize Go module and basic project structure
-  - [ ] Create PoW challenge structure and types
+  - [X] Create PoW challenge structure and types
-  - [ ] Set up testing framework and utilities
+  - [X] Set up testing framework and utilities
 
-- [ ] **Challenge Generation & HMAC Security**
+- [X] **Challenge Generation & HMAC Security**
-  - [ ] Implement HMAC-signed challenge generation (stateless)
+  - [X] Implement HMAC-signed challenge generation (stateless)
-  - [ ] Create challenge authenticity verification
+  - [X] Create challenge authenticity verification
-  - [ ] Add timestamp validation for replay protection (5 minutes TTL)
+  - [X] Add timestamp validation for replay protection (5 minutes TTL)
-  - [ ] Implement canonical challenge field ordering for HMAC
+  - [X] Implement canonical challenge field ordering for HMAC
-  - [ ] Add Base64URL encoding for HMAC signatures
+  - [X] Add Base64URL encoding for HMAC signatures (JSON handles this)
-  - [ ] Implement challenge string construction (`quotes:timestamp:difficulty:random`)
+  - [X] Implement challenge string construction (`quotes:timestamp:difficulty:random`)
 
-- [ ] **PoW Algorithm Implementation**
+- [X] **PoW Algorithm Implementation**
-  - [ ] Implement SHA-256 based PoW solution algorithm
+  - [X] Implement SHA-256 based PoW solution algorithm
-  - [ ] Implement leading zero bit counting for difficulty
+  - [X] Implement leading zero bit counting for difficulty
-  - [ ] Create nonce iteration and solution finding
+  - [X] Create nonce iteration and solution finding
-  - [ ] Add difficulty scaling (3-10 bits range)
+  - [X] Add difficulty scaling (3-10 bits range)
-  - [ ] Create challenge string format: `quotes:timestamp:difficulty:random:nonce`
+  - [X] Create challenge string format: `quotes:timestamp:difficulty:random:nonce`
-  - [ ] Implement hash verification for submitted solutions
+  - [X] Implement hash verification for submitted solutions
 
-- [ ] **Verification & Validation**
+- [X] **Verification & Validation**
-  - [ ] Create challenge verification logic with HMAC validation
+  - [X] Create challenge verification logic with HMAC validation
-  - [ ] Add solution validation against original challenge
+  - [X] Add solution validation against original challenge
-  - [ ] Test HMAC tamper detection and validation
+  - [X] Test HMAC tamper detection and validation
-  - [ ] Add difficulty adjustment mechanisms
+  - [X] Add difficulty adjustment mechanisms (config-based)
 
 - [ ] **Testing & Performance**
   - [ ] Unit tests for challenge generation and verification

go.mod

@@ -1,4 +1,4 @@
-module word-of-wisdom
+module hash-of-wisdom
 
 go 1.24.3
 

internal/pow/challenge/config.go

@@ -0,0 +1,147 @@
+package challenge
+
+import (
+	"crypto/rand"
+	"fmt"
+	"time"
+)
+
+// Config holds configuration for the PoW system
+type Config struct {
+	DefaultDifficulty     int           // Default difficulty in bits (e.g., 4)
+	MaxDifficulty         int           // Maximum allowed difficulty (e.g., 10)
+	MinDifficulty         int           // Minimum allowed difficulty (e.g., 3)
+	ChallengeTTL          time.Duration // Time-to-live for challenges (e.g., 5 minutes)
+	HMACSecret            []byte        // Secret key for HMAC signing
+	Resource              string        // Resource identifier (e.g., "quotes")
+	RandomBytes           int           // Number of random bytes in challenge (e.g., 6)
+	LoadAdjustmentBits    int           // Extra difficulty bits when server under load
+	FailurePenaltyBits    int           // Extra difficulty bits per failure group
+	MaxFailurePenaltyBits int           // Maximum failure penalty bits
+}
+
+// configOption represents a functional option for Config
+type configOption func(*Config)
+
+// WithDefaultDifficulty sets the default difficulty
+func WithDefaultDifficulty(difficulty int) configOption {
+	return func(c *Config) {
+		c.DefaultDifficulty = difficulty
+	}
+}
+
+// WithMaxDifficulty sets the maximum difficulty
+func WithMaxDifficulty(difficulty int) configOption {
+	return func(c *Config) {
+		c.MaxDifficulty = difficulty
+	}
+}
+
+// WithMinDifficulty sets the minimum difficulty
+func WithMinDifficulty(difficulty int) configOption {
+	return func(c *Config) {
+		c.MinDifficulty = difficulty
+	}
+}
+
+// WithChallengeTTL sets the challenge time-to-live
+func WithChallengeTTL(ttl time.Duration) configOption {
+	return func(c *Config) {
+		c.ChallengeTTL = ttl
+	}
+}
+
+// WithHMACSecret sets the HMAC secret
+func WithHMACSecret(secret []byte) configOption {
+	return func(c *Config) {
+		c.HMACSecret = secret
+	}
+}
+
+// WithResource sets the resource identifier
+func WithResource(resource string) configOption {
+	return func(c *Config) {
+		c.Resource = resource
+	}
+}
+
+// WithRandomBytes sets the number of random bytes
+func WithRandomBytes(bytes int) configOption {
+	return func(c *Config) {
+		c.RandomBytes = bytes
+	}
+}
+
+// WithLoadAdjustmentBits sets the load adjustment bits
+func WithLoadAdjustmentBits(bits int) configOption {
+	return func(c *Config) {
+		c.LoadAdjustmentBits = bits
+	}
+}
+
+// WithFailurePenaltyBits sets the failure penalty bits
+func WithFailurePenaltyBits(bits int) configOption {
+	return func(c *Config) {
+		c.FailurePenaltyBits = bits
+	}
+}
+
+// WithMaxFailurePenaltyBits sets the maximum failure penalty bits
+func WithMaxFailurePenaltyBits(bits int) configOption {
+	return func(c *Config) {
+		c.MaxFailurePenaltyBits = bits
+	}
+}
+
+// NewConfig creates and validates a new PoW configuration with defaults
+func NewConfig(opts ...configOption) (*Config, error) {
+	// Generate default HMAC secret
+	secret := make([]byte, 32)
+	rand.Read(secret)
+
+	// Create config with defaults
+	config := &Config{
+		DefaultDifficulty:     4,
+		MaxDifficulty:         10,
+		MinDifficulty:         3,
+		ChallengeTTL:          5 * time.Minute,
+		HMACSecret:            secret,
+		Resource:              "quotes",
+		RandomBytes:           6,
+		LoadAdjustmentBits:    1,
+		FailurePenaltyBits:    2,
+		MaxFailurePenaltyBits: 6,
+	}
+
+	// Apply options
+	for _, opt := range opts {
+		opt(config)
+	}
+
+	// Validate configuration
+	if config.RandomBytes <= 0 || config.RandomBytes > 32 {
+		return nil, fmt.Errorf("%w: random bytes must be between 1-32, got %d", ErrInvalidConfig, config.RandomBytes)
+	}
+
+	if config.MinDifficulty < 1 {
+		return nil, fmt.Errorf("%w: minimum difficulty must be >= 1, got %d", ErrInvalidConfig, config.MinDifficulty)
+	}
+
+	if config.MaxDifficulty < config.MinDifficulty {
+		return nil, fmt.Errorf("%w: maximum difficulty (%d) must be >= minimum difficulty (%d)", ErrInvalidConfig, config.MaxDifficulty, config.MinDifficulty)
+	}
+
+	if config.DefaultDifficulty < config.MinDifficulty || config.DefaultDifficulty > config.MaxDifficulty {
+		return nil, fmt.Errorf("%w: default difficulty (%d) must be between min (%d) and max (%d)", ErrInvalidConfig, config.DefaultDifficulty, config.MinDifficulty, config.MaxDifficulty)
+	}
+
+	if len(config.HMACSecret) == 0 {
+		return nil, fmt.Errorf("%w: HMAC secret cannot be empty", ErrInvalidConfig)
+	}
+
+	if config.ChallengeTTL <= 0 {
+		return nil, fmt.Errorf("%w: challenge TTL must be positive, got %v", ErrInvalidConfig, config.ChallengeTTL)
+	}
+
+	return config, nil
+}

internal/pow/challenge/generator.go

@@ -0,0 +1,62 @@
+package challenge
+
+import (
+	"crypto/rand"
+	"time"
+)
+
+// Generator handles creation of PoW challenges with HMAC signing
+type Generator struct {
+	config *Config
+}
+
+// GenerateOption represents a functional option for challenge generation
+type generateOption func(*Challenge)
+
+// WithDifficulty sets custom difficulty for the challenge
+func WithDifficulty(difficulty int) generateOption {
+	return func(c *Challenge) {
+		c.Difficulty = difficulty
+	}
+}
+
+// NewGenerator creates a new challenge generator
+func NewGenerator(config *Config) *Generator {
+	return &Generator{
+		config: config,
+	}
+}
+
+// GenerateChallenge creates a new HMAC-signed PoW challenge
+func (g *Generator) GenerateChallenge(opts ...generateOption) (*Challenge, error) {
+	// Create challenge with defaults (no random data yet)
+	challenge := &Challenge{
+		Timestamp:  time.Now().Unix(),
+		Difficulty: g.config.DefaultDifficulty,
+		Resource:   g.config.Resource,
+	}
+
+	// Apply options
+	for _, opt := range opts {
+		opt(challenge)
+	}
+
+	// Validate difficulty bounds
+	if challenge.Difficulty < g.config.MinDifficulty || challenge.Difficulty > g.config.MaxDifficulty {
+		return nil, ErrInvalidDifficulty
+	}
+
+	// Generate cryptographic random data
+	challenge.Random = g.generateRandom(g.config.RandomBytes)
+
+	// Sign the challenge with HMAC
+	challenge.Sign(g.config.HMACSecret)
+	return challenge, nil
+}
+
+// generateRandom creates cryptographic random bytes
+func (g *Generator) generateRandom(length int) []byte {
+	bytes := make([]byte, length)
+	rand.Read(bytes)
+	return bytes
+}

internal/pow/challenge/test_utils.go

@@ -1,4 +1,4 @@
-package pow
+package challenge
 
 import (
 	"crypto/rand"
@@ -11,17 +11,15 @@ func TestConfig() *Config {
 	secret := make([]byte, 32)
 	rand.Read(secret)
 
-	return &Config{
+	config, err := NewConfig(
-		DefaultDifficulty:     4,
+		WithHMACSecret(secret),
-		MaxDifficulty:         10,
+		WithDefaultDifficulty(4),
-		MinDifficulty:         3,
+		WithRandomBytes(6),
-		ChallengeTTL:          5 * time.Minute,
+	)
-		HMACSecret:            secret,
+	if err != nil {
-		Resource:              "quotes",
+		panic("Failed to create test config: " + err.Error())
-		LoadAdjustmentBits:    1,
-		FailurePenaltyBits:    2,
-		MaxFailurePenaltyBits: 6,
 	}
+	return config
 }
 
 // TestChallenge returns a valid challenge for testing
@@ -30,8 +28,8 @@ func TestChallenge() *Challenge {
 		Timestamp:  time.Now().Unix(),
 		Difficulty: 4,
 		Resource:   "quotes",
-		Random:     "a1b2c3d4e5f6",
+		Random:     []byte{0xa1, 0xb2, 0xc3, 0xd4, 0xe5, 0xf6},
-		HMAC:       "", // To be filled by generator
+		HMAC:       nil, // To be filled by generator
 	}
 }
 
@@ -39,7 +37,7 @@ func TestChallenge() *Challenge {
 func TestSolution() *Solution {
 	return &Solution{
 		Challenge: *TestChallenge(),
-		Nonce:     "42",
+		Nonce:     42,
 	}
 }
 

internal/pow/challenge/types.go

@@ -0,0 +1,134 @@
+package challenge
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// PoW package specific errors
+var (
+	ErrInvalidHMAC        = errors.New("challenge HMAC signature is invalid")
+	ErrExpiredChallenge   = errors.New("challenge has expired")
+	ErrInvalidSolution    = errors.New("proof of work solution is invalid")
+	ErrInvalidDifficulty  = errors.New("difficulty level is invalid")
+	ErrMalformedChallenge = errors.New("challenge format is malformed")
+	ErrInvalidConfig      = errors.New("configuration is invalid")
+)
+
+// Challenge represents a Proof of Work challenge with HMAC authentication
+type Challenge struct {
+	Timestamp  int64  `json:"timestamp"`
+	Difficulty int    `json:"difficulty"`
+	Resource   string `json:"resource"`
+	Random     []byte `json:"random"`
+	HMAC       []byte `json:"hmac"`
+}
+
+// CanonicalBytes returns the canonical byte representation for HMAC signing
+func (c *Challenge) CanonicalBytes() []byte {
+	// Use consistent field ordering: timestamp:difficulty:resource:random
+	buf := make([]byte, 0, 64)
+	buf = fmt.Appendf(buf, "%d:%d:%s:%x",
+		c.Timestamp,
+		c.Difficulty,
+		c.Resource,
+		c.Random,
+	)
+	return buf
+}
+
+// BuildSolutionString creates the string used for PoW computation
+func (c *Challenge) BuildSolutionString(nonce uint64) []byte {
+	// Format: resource:timestamp:difficulty:random:nonce
+	buf := make([]byte, 0, 64)
+	buf = fmt.Appendf(buf, "%s:%d:%d:%x:%d",
+		c.Resource,
+		c.Timestamp,
+		c.Difficulty,
+		c.Random,
+		nonce,
+	)
+	return buf
+}
+
+// VerifySolution verifies if a solution is valid for this challenge
+func (c *Challenge) VerifySolution(nonce uint64) bool {
+	// Build solution string
+	solutionStr := c.BuildSolutionString(nonce)
+
+	// Compute SHA-256 hash
+	hash := sha256.Sum256(solutionStr)
+
+	// Check if hash has required leading zero bits
+	return hasLeadingZeroBits(hash[:], c.Difficulty)
+}
+
+// hasLeadingZeroBits checks if hash has the required number of leading zero bits
+func hasLeadingZeroBits(hash []byte, difficulty int) bool {
+	full := difficulty >> 3        // number of whole zero bytes
+	rem  := uint(difficulty & 7)   // remaining leading zero bits
+
+	for i := range full {
+		if hash[i] != 0 {
+			return false
+		}
+	}
+	if rem == 0 {
+		return true
+	}
+	mask := byte(0xFF) << (8 - rem) // e.g., rem=3 => 11100000
+	return (hash[full] & mask) == 0
+}
+
+// IsExpired checks if challenge has exceeded TTL
+func (c *Challenge) IsExpired(ttl time.Duration) bool {
+	challengeTime := time.Unix(c.Timestamp, 0)
+	return time.Since(challengeTime) > ttl
+}
+
+// Sign creates and sets HMAC signature for the challenge
+func (c *Challenge) Sign(secret []byte) {
+	// Create canonical bytes for signing (excluding HMAC field)
+	canonical := c.CanonicalBytes()
+
+	// Create HMAC
+	h := hmac.New(sha256.New, secret)
+	h.Write(canonical)
+	c.HMAC = h.Sum(nil)
+}
+
+// VerifyHMAC verifies the HMAC signature of the challenge
+func (c *Challenge) VerifyHMAC(secret []byte) error {
+	if len(c.HMAC) == 0 {
+		return ErrMalformedChallenge
+	}
+
+	// Create canonical bytes (excluding HMAC)
+	canonical := c.CanonicalBytes()
+
+	// Compute expected HMAC
+	h := hmac.New(sha256.New, secret)
+	h.Write(canonical)
+	expectedSignature := h.Sum(nil)
+
+	// Compare signatures
+	if !hmac.Equal(c.HMAC, expectedSignature) {
+		return ErrInvalidHMAC
+	}
+
+	return nil
+}
+
+// Solution represents a client's solution to a PoW challenge
+type Solution struct {
+	Challenge Challenge `json:"challenge"`
+	Nonce     uint64    `json:"nonce"`
+}
+
+// Verify verifies if this solution is valid
+func (s *Solution) Verify() bool {
+	return s.Challenge.VerifySolution(s.Nonce)
+}

internal/pow/challenge/verifier.go

@@ -0,0 +1,28 @@
+package challenge
+
+// Verifier handles validation of PoW challenges
+type Verifier struct {
+	config *Config
+}
+
+// NewVerifier creates a new challenge verifier
+func NewVerifier(config *Config) *Verifier {
+	return &Verifier{
+		config: config,
+	}
+}
+
+// VerifyChallenge validates challenge authenticity and expiration
+func (v *Verifier) VerifyChallenge(challenge *Challenge) error {
+	// Check expiration first (cheap operation)
+	if challenge.IsExpired(v.config.ChallengeTTL) {
+		return ErrExpiredChallenge
+	}
+
+	// Check HMAC signature (expensive operation)
+	if err := challenge.VerifyHMAC(v.config.HMACSecret); err != nil {
+		return err
+	}
+
+	return nil
+}

internal/pow/generator.go

@@ -1,97 +0,0 @@
-package pow
-
-import (
-	"crypto/hmac"
-	"crypto/rand"
-	"crypto/sha256"
-	"encoding/base64"
-	"encoding/hex"
-	"fmt"
-	"time"
-)
-
-// Generator handles creation of PoW challenges with HMAC signing
-type Generator struct {
-	config *Config
-}
-
-// GenerateOption represents a functional option for challenge generation
-type generateOption func(*Challenge)
-
-// WithDifficulty sets custom difficulty for the challenge
-func WithDifficulty(difficulty int) generateOption {
-	return func(c *Challenge) {
-		c.Difficulty = difficulty
-	}
-}
-
-// NewGenerator creates a new challenge generator
-func NewGenerator(config *Config) *Generator {
-	return &Generator{
-		config: config,
-	}
-}
-
-// GenerateChallenge creates a new HMAC-signed PoW challenge
-func (g *Generator) GenerateChallenge(opts ...generateOption) (*Challenge, error) {
-	// Create challenge with defaults (no random data yet)
-	challenge := &Challenge{
-		Timestamp:  time.Now().Unix(),
-		Difficulty: g.config.DefaultDifficulty,
-		Resource:   g.config.Resource,
-	}
-
-	// Apply options
-	for _, opt := range opts {
-		opt(challenge)
-	}
-
-	// Validate difficulty bounds
-	if challenge.Difficulty < g.config.MinDifficulty || challenge.Difficulty > g.config.MaxDifficulty {
-		return nil, ErrInvalidDifficulty
-	}
-
-	// Generate cryptographic random data only after validation
-	challenge.Random = g.generateRandom(12) // 12 hex chars = 6 bytes
-
-	// Sign the challenge with HMAC
-	signature, err := g.signChallenge(challenge)
-	if err != nil {
-		return nil, fmt.Errorf("failed to sign challenge: %w", err)
-	}
-
-	challenge.HMAC = signature
-	return challenge, nil
-}
-
-// signChallenge creates HMAC signature for the challenge
-func (g *Generator) signChallenge(challenge *Challenge) (string, error) {
-	// Create canonical string for signing (excluding HMAC field)
-	canonical := g.canonicalChallengeString(challenge)
-
-	// Create HMAC
-	h := hmac.New(sha256.New, g.config.HMACSecret)
-	h.Write([]byte(canonical))
-	signature := h.Sum(nil)
-
-	// Return base64url encoded signature
-	return base64.RawURLEncoding.EncodeToString(signature), nil
-}
-
-// canonicalChallengeString creates a consistent string representation for HMAC
-func (g *Generator) canonicalChallengeString(challenge *Challenge) string {
-	// Use consistent field ordering: timestamp:difficulty:resource:random
-	return fmt.Sprintf("%d:%d:%s:%s",
-		challenge.Timestamp,
-		challenge.Difficulty,
-		challenge.Resource,
-		challenge.Random,
-	)
-}
-
-// generateRandom creates cryptographic random hex string
-func (g *Generator) generateRandom(length int) string {
-	bytes := make([]byte, length/2)
-	rand.Read(bytes)
-	return hex.EncodeToString(bytes)
-}

internal/pow/solver/solver.go

@@ -0,0 +1,94 @@
+package solver
+
+import (
+	"context"
+	"runtime"
+	"sync/atomic"
+
+	"word-of-wisdom/internal/pow/challenge"
+)
+
+// Solver handles parallel PoW solving with configurable parallelism
+type Solver struct {
+	workers int
+}
+
+// SolverOption represents functional options for solver configuration
+type solverOption func(*Solver)
+
+// WithWorkers sets the number of parallel workers
+func WithWorkers(workers int) solverOption {
+	return func(s *Solver) {
+		s.workers = workers
+	}
+}
+
+// NewSolver creates a new parallel PoW solver
+func NewSolver(options ...solverOption) *Solver {
+	solver := &Solver{
+		workers: runtime.NumCPU(), // Default to CPU count
+	}
+
+	for _, option := range options {
+		option(solver)
+	}
+
+	return solver
+}
+
+// Solve attempts to find a valid nonce for the given challenge
+func (s *Solver) Solve(ctx context.Context, ch *challenge.Challenge) (*challenge.Solution, error) {
+	// Create cancellable context for workers
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	// Channel to receive solution from any worker
+	solutionCh := make(chan *challenge.Solution, 1)
+
+	// Shared nonce counter for work distribution
+	var nonceCounter atomic.Uint64
+
+	// Start parallel workers
+	for i := range s.workers {
+		go func(workerID int) {
+			s.worker(ctx, ch, &nonceCounter, solutionCh)
+		}(i)
+	}
+
+	// Wait for either solution or context cancellation
+	select {
+	case solution := <-solutionCh:
+		return solution, nil
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
+// worker performs PoW computation in parallel
+func (s *Solver) worker(ctx context.Context, ch *challenge.Challenge, nonceCounter *atomic.Uint64, solutionCh chan<- *challenge.Solution) {
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+			// Get next nonce to try
+			nonce := nonceCounter.Add(1) - 1
+
+			// Try this nonce
+			if ch.VerifySolution(nonce) {
+				// Found solution! Send it back
+				solution := &challenge.Solution{
+					Challenge: *ch,
+					Nonce:     nonce,
+				}
+
+				select {
+				case solutionCh <- solution:
+				case <-ctx.Done():
+				}
+				return
+			}
+		}
+	}
+}

internal/pow/types.go

@@ -1,53 +0,0 @@
-package pow
-
-import (
-	"errors"
-	"time"
-)
-
-// PoW package specific errors
-var (
-	ErrInvalidHMAC      = errors.New("challenge HMAC signature is invalid")
-	ErrExpiredChallenge = errors.New("challenge has expired")
-	ErrInvalidSolution  = errors.New("proof of work solution is invalid")
-	ErrInvalidDifficulty = errors.New("difficulty level is invalid")
-	ErrMalformedChallenge = errors.New("challenge format is malformed")
-)
-
-// Challenge represents a Proof of Work challenge with HMAC authentication
-type Challenge struct {
-	Timestamp  int64  `json:"timestamp"`
-	Difficulty int    `json:"difficulty"`
-	Resource   string `json:"resource"`
-	Random     string `json:"random"`
-	HMAC       string `json:"hmac"`
-}
-
-// Solution represents a client's solution to a PoW challenge
-type Solution struct {
-	Challenge Challenge `json:"challenge"`
-	Nonce     string    `json:"nonce"`
-}
-
-// ChallengeRequest represents a request for a new challenge
-type ChallengeRequest struct{}
-
-// SolutionRequest represents a client's submission of a solved challenge
-type SolutionRequest struct {
-	Challenge Challenge `json:"challenge"`
-	Nonce     string    `json:"nonce"`
-}
-
-// Config holds configuration for the PoW system
-type Config struct {
-	DefaultDifficulty     int           // Default difficulty in bits (e.g., 4)
-	MaxDifficulty         int           // Maximum allowed difficulty (e.g., 10)
-	MinDifficulty         int           // Minimum allowed difficulty (e.g., 3)
-	ChallengeTTL          time.Duration // Time-to-live for challenges (e.g., 5 minutes)
-	HMACSecret            []byte        // Secret key for HMAC signing
-	Resource              string        // Resource identifier (e.g., "quotes")
-	LoadAdjustmentBits    int           // Extra difficulty bits when server under load
-	FailurePenaltyBits    int           // Extra difficulty bits per failure group
-	MaxFailurePenaltyBits int           // Maximum failure penalty bits
-}
-