# KMS Security Architecture

## Table of Contents
1. [Security Overview](#security-overview)
2. [Multi-Layered Security Model](#multi-layered-security-model)
3. [Authentication Security](#authentication-security)
4. [Token Security Models](#token-security-models)
5. [Authorization Framework](#authorization-framework)
6. [Data Protection](#data-protection)
7. [Security Middleware Chain](#security-middleware-chain)
8. [Threat Model](#threat-model)
9. [Security Controls](#security-controls)
10. [Compliance Framework](#compliance-framework)

---

## Security Overview

The KMS implements a comprehensive security architecture based on defense-in-depth principles. Every layer of the system includes security controls designed to protect against both external threats and insider risks.

### Security Objectives
- **Confidentiality**: Protect sensitive data and credentials
- **Integrity**: Ensure data accuracy and prevent tampering
- **Availability**: Maintain service availability under attack
- **Accountability**: Complete audit trail of all operations
- **Non-repudiation**: Cryptographic proof of operations

### Security Principles
- **Zero Trust**: Verify every request regardless of source
- **Fail Secure**: Safe defaults when systems fail
- **Defense in Depth**: Multiple security layers
- **Least Privilege**: Minimal permission grants
- **Security by Design**: Security integrated into architecture

---

## Multi-Layered Security Model

```mermaid
graph TB
    subgraph "External Threats"
        DDoS[DDoS Attacks]
        XSS[XSS Attacks]
        CSRF[CSRF Attacks]
        Injection[SQL Injection]
        AuthBypass[Auth Bypass]
        TokenReplay[Token Replay]
        BruteForce[Brute Force]
    end
    
    subgraph "Security Perimeter"
        subgraph "Load Balancer Security"
            NginxSec[Nginx Security<br/>- Rate limiting<br/>- SSL termination<br/>- Request filtering]
        end
        
        subgraph "Application Security Layer"
            SecurityMW[Security Middleware]
            
            subgraph "Security Headers"
                HSTS[HSTS Header<br/>max-age=31536000]
                ContentType[Content-Type-Options<br/>nosniff]
                FrameOptions[X-Frame-Options<br/>DENY]
                XSSProtection[XSS-Protection<br/>1; mode=block]
                CSP[Content-Security-Policy<br/>Restrictive policy]
            end
            
            subgraph "CORS Protection"
                Origins[Allowed Origins<br/>Whitelist validation]
                Methods[Allowed Methods<br/>GET, POST, PUT, DELETE]
                Headers[Allowed Headers<br/>Authorization, Content-Type]
                Credentials[Credentials Policy<br/>Same-origin only]
            end
            
            subgraph "CSRF Protection"
                CSRFToken[CSRF Token<br/>Double-submit cookie]
                CSRFHeader[X-CSRF-Token<br/>Header validation]
                SameSite[SameSite Cookie<br/>Strict policy]
            end
        end
        
        subgraph "Rate Limiting Defense"
            GlobalLimit[Global Rate Limit<br/>100 RPS per IP]
            EndpointLimit[Endpoint-specific<br/>Limits per route]
            BurstControl[Burst Control<br/>200 request burst]
            Backoff[Exponential Backoff<br/>Failed attempts]
        end
        
        subgraph "Authentication Security"
            MultiAuth[Multi-Provider Auth<br/>Header, JWT, OAuth2, SAML]
            
            subgraph "Token Security"
                JWTSigning[JWT Signing<br/>RS256 Algorithm]
                TokenExpiry[Token Expiration<br/>Configurable TTL]
                TokenRevocation[Token Revocation<br/>Blacklist in Redis]
                TokenRotation[Token Rotation<br/>Refresh mechanism]
            end
            
            subgraph "Static Token Security"
                HMACValidation[HMAC Validation<br/>SHA-256 signature]
                TimestampCheck[Timestamp Validation<br/>5-minute window]
                ReplayProtection[Replay Protection<br/>Nonce tracking]
                KeyRotation[Key Rotation<br/>Configurable schedule]
            end
            
            subgraph "Session Security"
                SessionEncryption[Session Encryption<br/>AES-256-GCM]
                SessionTimeout[Session Timeout<br/>Idle timeout]
                SessionFixation[Session Fixation<br/>Protection]
            end
        end
        
        subgraph "Authorization Security"
            RBAC[Role-Based Access<br/>Hierarchical permissions]
            PermissionCheck[Permission Validation<br/>Request-level checks]
            ScopeValidation[Scope Validation<br/>Token scope matching]
            PrincipleOfLeastPrivilege[Least Privilege<br/>Minimal permissions]
        end
        
        subgraph "Data Protection"
            Encryption[Data Encryption]
            
            subgraph "Encryption at Rest"
                DBEncryption[Database Encryption<br/>AES-256 column encryption]
                KeyStorage[Key Management<br/>Environment variables]
                SaltedHashing[Salted Hashing<br/>BCrypt cost 14]
            end
            
            subgraph "Encryption in Transit"
                TLS13[TLS 1.3<br/>All communications]
                CertPinning[Certificate Pinning<br/>OAuth2/SAML providers]
                MTLS[Mutual TLS<br/>Service-to-service]
            end
        end
        
        subgraph "Input Validation"
            JSONValidation[JSON Schema<br/>Request validation]
            SQLProtection[SQL Injection<br/>Parameterized queries]
            XSSProtectionValidation[XSS Protection<br/>Input sanitization]
            PathTraversal[Path Traversal<br/>Prevention]
        end
        
        subgraph "Monitoring & Detection"
            SecurityAudit[Security Audit Log<br/>All operations logged]
            FailureDetection[Failure Detection<br/>Failed auth attempts]
            AnomalyDetection[Anomaly Detection<br/>Unusual patterns]
            AlertSystem[Alert System<br/>Security incidents]
        end
    end
    
    subgraph "Database Security"
        DBSecurity[PostgreSQL Security<br/>- Connection encryption<br/>- User isolation<br/>- Query logging<br/>- Backup encryption]
    end
    
    subgraph "Infrastructure Security"
        ContainerSecurity[Container Security<br/>- Non-root user<br/>- Minimal images<br/>- Security scanning]
        NetworkSecurity[Network Security<br/>- Internal networks<br/>- Firewall rules<br/>- VPN access]
    end
    
    %% Threat Mitigation Connections
    DDoS -.->|Mitigated by| NginxSec
    XSS -.->|Prevented by| SecurityMW
    CSRF -.->|Blocked by| CSRFToken
    Injection -.->|Stopped by| JSONValidation
    AuthBypass -.->|Blocked by| MultiAuth
    TokenReplay -.->|Prevented by| TimestampCheck
    BruteForce -.->|Limited by| GlobalLimit
    
    %% Security Layer Flow
    NginxSec --> SecurityMW
    SecurityMW --> GlobalLimit
    GlobalLimit --> MultiAuth
    MultiAuth --> RBAC
    RBAC --> Encryption
    Encryption --> JSONValidation
    JSONValidation --> SecurityAudit
    
    SecurityAudit --> DBSecurity
    SecurityAudit --> ContainerSecurity
    
    %% Styling
    classDef threat fill:#ffcdd2,stroke:#d32f2f,stroke-width:2px
    classDef security fill:#c8e6c9,stroke:#388e3c,stroke-width:2px
    classDef auth fill:#e1bee7,stroke:#7b1fa2,stroke-width:2px
    classDef data fill:#fff9c4,stroke:#f57f17,stroke-width:2px
    classDef infra fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
    
    class DDoS,XSS,CSRF,Injection,AuthBypass,TokenReplay,BruteForce threat
    class SecurityMW,HSTS,ContentType,FrameOptions,XSSProtection,CSP,Origins,Methods,Headers,Credentials,CSRFToken,CSRFHeader,SameSite security
    class MultiAuth,JWTSigning,TokenExpiry,TokenRevocation,TokenRotation,HMACValidation,TimestampCheck,ReplayProtection,KeyRotation,SessionEncryption,SessionTimeout,SessionFixation,RBAC,PermissionCheck,ScopeValidation,PrincipleOfLeastPrivilege auth
    class Encryption,DBEncryption,KeyStorage,SaltedHashing,TLS13,CertPinning,MTLS,JSONValidation,SQLProtection,XSSProtectionValidation,PathTraversal,SecurityAudit,FailureDetection,AnomalyDetection,AlertSystem,DBSecurity data
    class ContainerSecurity,NetworkSecurity,NginxSec,GlobalLimit,EndpointLimit,BurstControl,Backoff infra
```

### Security Layer Breakdown

1. **Perimeter Security**: Load balancer, rate limiting, DDoS protection
2. **Application Security**: Security headers, CORS, CSRF protection
3. **Authentication Security**: Multi-provider authentication with strong cryptography
4. **Authorization Security**: RBAC with hierarchical permissions
5. **Data Protection**: Encryption at rest and in transit
6. **Input Validation**: Comprehensive input sanitization and validation
7. **Monitoring**: Security event detection and alerting

---

## Authentication Security

### Multi-Provider Authentication Framework

The KMS supports four authentication providers, each with specific security controls:

#### **Header-based Authentication**
```go
// File: internal/auth/header_validator.go:42
func (hv *HeaderValidator) ValidateAuthenticationHeaders(r *http.Request) (*ValidatedUserContext, error)
```

**Security Features:**
- **HMAC-SHA256 Signatures**: Request integrity validation
- **Timestamp Validation**: 5-minute window prevents replay attacks
- **Constant-time Comparison**: Prevents timing attacks
- **Email Format Validation**: Prevents injection attacks

**Implementation Details:**
```go
// HMAC signature validation with constant-time comparison
func (hv *HeaderValidator) validateSignature(userEmail, timestamp, signature string) bool {
    mac := hmac.New(sha256.New, []byte(signingKey))
    mac.Write([]byte(signingString))
    expectedSignature := hex.EncodeToString(mac.Sum(nil))
    return hmac.Equal([]byte(signature), []byte(expectedSignature))
}
```

#### **JWT Authentication**
```go
// File: internal/auth/jwt.go:47
func (j *JWTManager) GenerateToken(userToken *domain.UserToken) (string, error)
```

**Security Features:**
- **RSA Signatures**: Strong cryptographic signing
- **Token Revocation**: Redis-backed blacklist
- **Secure JTI Generation**: Cryptographically secure token IDs
- **Claims Validation**: Complete token verification

**Token Structure:**
```json
{
  "iss": "kms-api-service",
  "sub": "user@example.com",
  "aud": ["app-id"],
  "exp": 1642781234,
  "iat": 1642694834,
  "nbf": 1642694834,
  "jti": "secure-random-id",
  "user_id": "user@example.com",
  "app_id": "app-id",
  "permissions": ["app.read", "token.create"],
  "token_type": "user",
  "max_valid_at": 1643299634
}
```

#### **OAuth2 Authentication**
```go
// File: internal/auth/oauth2.go
```

**Security Features:**
- **Authorization Code Flow**: Secure OAuth2 flow implementation
- **State Parameter**: CSRF protection for OAuth2
- **Token Exchange**: Secure credential handling
- **Provider Validation**: Certificate pinning support

#### **SAML Authentication**
```go
// File: internal/auth/saml.go
```

**Security Features:**
- **XML Signature Validation**: Assertion integrity verification
- **Certificate Validation**: Provider certificate verification
- **Attribute Extraction**: Secure claim processing
- **Replay Protection**: Timestamp and nonce validation

---

## Token Security Models

### Static Token Security (HMAC-based)

```mermaid
stateDiagram-v2
    [*] --> TokenRequest: Client requests token
    
    state TokenRequest {
        [*] --> ValidateApp: Validate app_id
        ValidateApp --> ValidatePerms: Check permissions
        ValidatePerms --> GenerateToken: Create token
        GenerateToken --> [*]
    }
    
    TokenRequest --> StaticToken: type=static
    
    state StaticToken {
        [*] --> GenerateHMAC: Generate HMAC key
        GenerateHMAC --> HashKey: BCrypt hash (cost 14)
        HashKey --> StoreDB: Store in static_tokens table
        StoreDB --> GrantPerms: Assign permissions
        GrantPerms --> Active: Token ready
        
        Active --> Verify: Incoming request
        Verify --> ValidateHMAC: Check HMAC signature
        ValidateHMAC --> CheckTimestamp: Replay protection
        CheckTimestamp --> CheckPerms: Validate permissions
        CheckPerms --> Authorized: Permission check
        CheckPerms --> Denied: Permission denied
        
        Active --> Revoke: Admin action
        Revoke --> Revoked: Update granted_permissions.revoked=true
    }
    
    Authorized --> TokenResponse: Success response
    Denied --> ErrorResponse: Error response
    Revoked --> [*]: Token lifecycle end
    
    note right of StaticToken
        Static tokens use HMAC signatures
        - Timestamp-based replay protection
        - BCrypt hashed storage
        - Permission-based access control
        - No expiration (until revoked)
    end note
```

#### **Token Format**
```
Format: {PREFIX}_{BASE64_DATA}
Example: ABC_xyz123base64encodeddata...
Validation: HMAC-SHA256(request_data, hmac_key)
Storage: BCrypt hash (cost 14)
Lifetime: No expiration (until revoked)
```

#### **Security Implementation**
```go
// File: internal/crypto/token.go:95
func (tg *TokenGenerator) HashToken(token string) (string, error) {
    hash, err := bcrypt.GenerateFromPassword([]byte(token), tg.bcryptCost)
    if err != nil {
        return "", fmt.Errorf("failed to hash token with bcrypt cost %d: %w", tg.bcryptCost, err)
    }
    return string(hash), nil
}
```

### User Token Security (JWT-based)

```mermaid
stateDiagram-v2
    [*] --> UserTokenRequest: User requests token
    
    state UserTokenRequest {
        [*] --> AuthUser: Authenticate user
        AuthUser --> GenerateJWT: Create JWT with claims
        GenerateJWT --> SetExpiry: Set expires_at, max_valid_at
        SetExpiry --> StoreSession: Store user session
        StoreSession --> Active: JWT issued
    }
    
    UserTokenRequest --> UserToken: type=user
    
    state UserToken {
        Active --> Verify: Incoming request
        Verify --> ValidateJWT: Check JWT signature
        ValidateJWT --> CheckExpiry: Verify expiration
        CheckExpiry --> CheckRevoked: Check revocation list
        CheckRevoked --> Authorized: Valid token
        CheckRevoked --> Denied: Token invalid
        CheckExpiry --> Expired: Token expired
        
        Active --> Renew: Renewal request
        Renew --> CheckRenewal: Within renewal window?
        CheckRenewal --> GenerateNew: Issue new JWT
        CheckRenewal --> Denied: Renewal denied
        GenerateNew --> Active: New token active
        
        Active --> Logout: User logout
        Logout --> Revoked: Add to revocation list
        
        Expired --> Renew: Attempt renewal
    }
    
    Authorized --> TokenResponse: Success response
    Denied --> ErrorResponse: Error response
    Revoked --> [*]: Token lifecycle end
    
    note right of UserToken
        User tokens are JWT-based
        - Configurable expiration
        - Renewable within limits
        - Session tracking
        - Hierarchical permissions
    end note
```

#### **Token Format**
```
Format: {CUSTOM_PREFIX}UT-{JWT_TOKEN}
Example: ABC123UT-eyJhbGciOiJSUzI1NiIs...
Validation: RSA signature + claims validation
Storage: Revocation list in Redis
Lifetime: Configurable with renewal window
```

#### **Security Features**
- **RSA-256 Signatures**: Strong cryptographic validation
- **Token Revocation**: Redis blacklist with TTL
- **Renewal Controls**: Limited renewal window
- **Session Tracking**: Database session management

---

## Authorization Framework

### Role-Based Access Control (RBAC)

The KMS implements a hierarchical permission system with role-based access control:

#### **Permission Hierarchy**
```
admin
├── app.admin
│   ├── app.read
│   ├── app.write
│   │   ├── app.create
│   │   ├── app.update
│   │   └── app.delete
├── token.admin
│   ├── token.read
│   │   └── token.verify
│   ├── token.write
│   │   ├── token.create
│   │   └── token.revoke
├── permission.admin
│   ├── permission.read
│   ├── permission.write
│   │   ├── permission.grant
│   │   └── permission.revoke
└── user.admin
    ├── user.read
    └── user.write
```

#### **Role Definitions**
```go
// File: internal/auth/permissions.go:151
func (h *PermissionHierarchy) initializeDefaultRoles() {
    defaultRoles := []*Role{
        {
            Name:        "super_admin",
            Description: "Super administrator with full access",
            Permissions: []string{"admin"},
            Metadata:    map[string]string{"level": "system"},
        },
        {
            Name:        "app_admin", 
            Description: "Application administrator",
            Permissions: []string{"app.admin", "token.admin", "user.read"},
            Metadata:    map[string]string{"level": "application"},
        },
        // Additional roles...
    }
}
```

#### **Permission Evaluation**
```go
// File: internal/auth/permissions.go:201
func (pm *PermissionManager) HasPermission(ctx context.Context, userID, appID, permission string) (*PermissionEvaluation, error) {
    // Cache lookup first
    cacheKey := cache.CacheKey(cache.KeyPrefixPermission, fmt.Sprintf("%s:%s:%s", userID, appID, permission))
    
    // Evaluate permission with hierarchy
    evaluation := pm.evaluatePermission(ctx, userID, appID, permission)
    
    // Cache result for 5 minutes
    pm.cacheManager.SetJSON(ctx, cacheKey, evaluation, 5*time.Minute)
    
    return evaluation, nil
}
```

### Authorization Controls

#### **Resource Ownership**
```go
// File: internal/authorization/rbac.go:100
func (a *AuthorizationService) AuthorizeApplicationOwnership(userID string, app *domain.Application) error {
    // System admins can access any application
    if a.isSystemAdmin(userID) {
        return nil
    }
    
    // Check if user is the owner
    if a.isOwner(userID, &app.Owner) {
        return nil
    }
    
    return errors.NewForbiddenError("You do not have permission to access this application")
}
```

#### **Token Scoping**
```go
// File: internal/services/token_service.go:400
func (s *tokenService) verifyStaticToken(ctx context.Context, req *domain.VerifyRequest, app *domain.Application) (*domain.VerifyResponse, error) {
    // Get granted permissions for this token
    permissions, err := s.grantRepo.GetGrantedPermissionScopes(ctx, domain.TokenTypeStatic, matchedToken.ID)
    
    // Check specific permissions if requested
    if len(req.Permissions) > 0 {
        permissionResults, err := s.grantRepo.HasAnyPermission(ctx, domain.TokenTypeStatic, matchedToken.ID, req.Permissions)
        // Validate all requested permissions are granted
    }
}
```

---

## Data Protection

### Encryption at Rest

#### **Database Encryption**
```sql
-- Sensitive data encryption in PostgreSQL
CREATE TABLE applications (
    app_id VARCHAR(100) PRIMARY KEY,
    hmac_key TEXT, -- Encrypted with application-level encryption
    created_at TIMESTAMP DEFAULT NOW()
);

CREATE TABLE static_tokens (
    id UUID PRIMARY KEY,
    key_hash TEXT NOT NULL, -- BCrypt hashed with cost 14
    created_at TIMESTAMP DEFAULT NOW()
);
```

#### **BCrypt Hashing**
```go
// File: internal/crypto/token.go:22
const BcryptCost = 14 // 2025 security standards (minimum 14)

func (tg *TokenGenerator) HashToken(token string) (string, error) {
    hash, err := bcrypt.GenerateFromPassword([]byte(token), tg.bcryptCost)
    if err != nil {
        return "", fmt.Errorf("failed to hash token with bcrypt cost %d: %w", tg.bcryptCost, err)
    }
    return string(hash), nil
}
```

### Encryption in Transit

#### **TLS Configuration**
```go
// TLS 1.3 configuration for all communications
tlsConfig := &tls.Config{
    MinVersion: tls.VersionTLS13,
    CipherSuites: []uint16{
        tls.TLS_AES_256_GCM_SHA384,
        tls.TLS_CHACHA20_POLY1305_SHA256,
        tls.TLS_AES_128_GCM_SHA256,
    },
}
```

#### **Certificate Pinning**
```go
// OAuth2/SAML provider certificate pinning
func (o *OAuth2Provider) validateCertificate(cert *x509.Certificate) error {
    expectedFingerprints := o.config.GetStringSlice("OAUTH2_CERT_FINGERPRINTS")
    
    fingerprint := sha256.Sum256(cert.Raw)
    fingerprintHex := hex.EncodeToString(fingerprint[:])
    
    for _, expected := range expectedFingerprints {
        if fingerprintHex == expected {
            return nil
        }
    }
    
    return fmt.Errorf("certificate fingerprint mismatch")
}
```

---

## Security Middleware Chain

### Middleware Processing Order

1. **Request Logger**: Structured logging with security context
2. **Security Headers**: XSS, clickjacking, MIME-type protection
3. **CORS Handler**: Cross-origin request validation
4. **CSRF Protection**: Double-submit token validation
5. **Rate Limiter**: DDoS and abuse protection
6. **Authentication**: Multi-provider authentication
7. **Authorization**: Permission validation
8. **Input Validation**: Request sanitization and validation

### Rate Limiting Implementation

```go
// File: internal/middleware/security.go:48
func (s *SecurityMiddleware) RateLimitMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        clientIP := s.getClientIP(r)
        limiter := s.getRateLimiter(clientIP)
        
        if !limiter.Allow() {
            s.logger.Warn("Rate limit exceeded", 
                zap.String("client_ip", clientIP),
                zap.String("path", r.URL.Path))
            
            s.trackRateLimitViolation(clientIP)
            
            http.Error(w, `{"error":"rate_limit_exceeded"}`, http.StatusTooManyRequests)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}
```

### Brute Force Protection

```go
// File: internal/middleware/security.go:365
func (s *SecurityMiddleware) checkAndBlockIP(clientIP string) {
    var count int
    err := s.cacheManager.GetJSON(ctx, key, &count)
    
    maxFailures := s.config.GetInt("MAX_AUTH_FAILURES")
    if maxFailures <= 0 {
        maxFailures = 5 // Default
    }
    
    if count >= maxFailures {
        // Block the IP for 1 hour
        blockInfo := map[string]interface{}{
            "blocked_at":     time.Now().Unix(),
            "failure_count":  count,
            "reason":         "excessive_auth_failures",
        }
        
        s.cacheManager.SetJSON(ctx, blockKey, blockInfo, blockDuration)
    }
}
```

---

## Threat Model

### External Threats

#### **Network-based Attacks**
- **DDoS**: Rate limiting and load balancer protection
- **Man-in-the-Middle**: TLS 1.3 encryption
- **Packet Sniffing**: End-to-end encryption

#### **Application-level Attacks**
- **SQL Injection**: Parameterized queries only
- **XSS**: Input validation and CSP headers
- **CSRF**: Double-submit token protection
- **Session Hijacking**: Secure session management

#### **Authentication Attacks**
- **Brute Force**: Rate limiting and account lockout
- **Credential Stuffing**: Multi-factor authentication support
- **Token Replay**: Timestamp validation and nonces
- **JWT Attacks**: Strong cryptographic signing

### Insider Threats

#### **Privileged User Abuse**
- **Audit Logging**: Complete audit trail
- **Role Separation**: Principle of least privilege
- **Session Monitoring**: Abnormal activity detection

#### **Data Exfiltration**
- **Access Controls**: Resource-level authorization
- **Data Classification**: Sensitive data identification
- **Export Monitoring**: Large data access alerts

---

## Security Controls

### Preventive Controls

#### **Authentication Controls**
- Multi-factor authentication support
- Strong password policies (where applicable)
- Account lockout mechanisms
- Session timeout enforcement

#### **Authorization Controls**
- Role-based access control (RBAC)
- Resource-level permissions
- API endpoint protection
- Ownership validation

#### **Data Protection Controls**
- Encryption at rest (AES-256)
- Encryption in transit (TLS 1.3)
- Key management procedures
- Secure data disposal

### Detective Controls

#### **Monitoring and Logging**
```go
// Comprehensive audit logging
type AuditLog struct {
    ID           uuid.UUID         `json:"id"`
    Timestamp    time.Time         `json:"timestamp"`
    UserID       string            `json:"user_id"`
    Action       string            `json:"action"`
    ResourceType string            `json:"resource_type"`
    ResourceID   string            `json:"resource_id"`
    IPAddress    string            `json:"ip_address"`
    UserAgent    string            `json:"user_agent"`
    Metadata     map[string]interface{} `json:"metadata"`
}
```

#### **Security Event Detection**
- Failed authentication attempts
- Privilege escalation attempts
- Unusual access patterns
- Token misuse detection

### Responsive Controls

#### **Incident Response**
- Automated threat response
- Token revocation procedures
- User account suspension
- Alert escalation workflows

#### **Recovery Controls**
- Backup and restore procedures
- Disaster recovery planning
- Business continuity measures
- Data integrity verification

---

## Compliance Framework

### OWASP Top 10 Protection

1. **Injection**: Parameterized queries, input validation
2. **Broken Authentication**: Multi-provider auth, strong crypto
3. **Sensitive Data Exposure**: Encryption, secure storage
4. **XML External Entities**: JSON-only API
5. **Broken Access Control**: RBAC, authorization checks
6. **Security Misconfiguration**: Secure defaults
7. **Cross-Site Scripting**: Input validation, CSP
8. **Insecure Deserialization**: Safe JSON handling
9. **Known Vulnerabilities**: Regular dependency updates
10. **Logging & Monitoring**: Comprehensive audit trails

### Regulatory Compliance

#### **SOC 2 Type II Controls**
- **Security**: Access controls, encryption, monitoring
- **Availability**: High availability, disaster recovery
- **Processing Integrity**: Data validation, error handling
- **Confidentiality**: Data classification, access restrictions
- **Privacy**: Data minimization, consent management

#### **GDPR Compliance** (where applicable)
- **Data Protection by Design**: Privacy-first architecture
- **Consent Management**: Granular consent controls
- **Right to Erasure**: Data deletion procedures
- **Data Portability**: Export capabilities
- **Breach Notification**: Automated incident response

#### **NIST Cybersecurity Framework**
- **Identify**: Asset inventory, risk assessment
- **Protect**: Access controls, data security
- **Detect**: Monitoring, anomaly detection
- **Respond**: Incident response procedures
- **Recover**: Business continuity planning

### Security Metrics

#### **Key Security Indicators**
- Authentication success/failure rates
- Authorization denial rates
- Token usage patterns
- Security event frequency
- Incident response times

#### **Security Monitoring**
```yaml
alerts:
  - name: "High Authentication Failure Rate"
    condition: "auth_failures > 10 per minute per IP"
    severity: "warning"
    
  - name: "Privilege Escalation Attempt"
    condition: "permission_denied + elevated_permission"
    severity: "critical"
    
  - name: "Token Abuse Detection"
    condition: "token_usage_anomaly"
    severity: "warning"
```

This security architecture document provides comprehensive coverage of the KMS security model, suitable for security audits, compliance reviews, and security team training.