20-hashes-and-encoding

Cryptographic Hashes and Encoding in Go

This example demonstrates cryptographic hash functions and various encoding methods in Go, including secure hashing algorithms, HMAC, and different encoding formats.

Key Components

1. Hash Functions

• SHA-256 implementation
• SHA-512 implementation
• SHA-1 (with security warnings)
• MD5 (with security warnings)
• Streaming hash computation

2. HMAC (Hash-based Message Authentication Code)

• HMAC-SHA256 implementation
• HMAC-SHA512 implementation
• Message verification
• Security considerations

3. Common Hashing Patterns

• Multiple item hashing
• Password hashing with salt
• File hashing
• Stream processing

4. Base64 Encoding

• Standard Base64
• URL-safe Base64
• Raw Base64 (no padding)
• Custom Base64 alphabets
• Encoding/decoding operations

5. Base32 Encoding

• Standard Base32
• Hex Base32
• Custom Base32 alphabets
• Padding options

6. Hex Encoding

• Standard hex encoding
• Hex dumps
• Binary-to-hex conversion

Best Practices

1. Cryptographic Hashing

   • Use SHA-256 or SHA-512 for new applications
   • Avoid MD5 and SHA-1 for security-critical operations
   • Always handle hash computation errors
   • Use streaming for large data

2. HMAC Usage

   • Keep keys secure and private
   • Use cryptographically secure key generation
   • Implement constant-time comparisons
   • Handle all error cases

3. Encoding

   • Choose appropriate encoding for the use case
   • Handle padding correctly
   • Validate input before decoding
   • Consider URL safety when needed

Memory Considerations

1. Hash Computation

   • Buffer management for streaming
   • Memory usage in hash state
   • Output size considerations
   • Cleanup of sensitive data

2. HMAC Operations

   • Key storage security
   • Memory cleanup after use
   • Buffer reuse strategies
   • Resource management

3. Encoding Operations

   • Output size calculations
   • Buffer pre-allocation
   • Memory efficiency in conversions
   • Streaming for large data

Common Patterns

1. File Hashing

   hash := sha256.New()
   if _, err := io.Copy(hash, file); err != nil {
       // Handle error
   }
   sum := hash.Sum(nil)
   

2. Password Hashing

   hash := sha256.New()
   hash.Write(salt)
   hash.Write(password)
   hashedPassword := hash.Sum(nil)
   

3. Base64 Encoding

   encoded := base64.StdEncoding.EncodeToString(data)
   decoded, err := base64.StdEncoding.DecodeString(encoded)
   

Safety Considerations

1. Cryptographic Security

   • Use cryptographically secure algorithms
   • Keep keys and sensitive data secure
   • Implement proper error handling
   • Consider timing attacks

2. Input Validation

   • Validate input sizes
   • Check for malformed data
   • Handle decoding errors
   • Sanitize output when needed

3. Resource Management

   • Clean up sensitive data
   • Handle large inputs safely
   • Manage memory efficiently
   • Close resources properly

Testing Considerations

1. Hash Testing

   • Test known input/output pairs
   • Test streaming operations
   • Test error conditions
   • Test with different sizes

2. HMAC Testing

   • Test with various keys
   • Test verification
   • Test tampering detection
   • Test error cases

3. Encoding Testing

   • Test encoding/decoding pairs
   • Test special characters
   • Test padding cases
   • Test error handling

Common Use Cases

1. Data Integrity

   • File checksums
   • Message verification
   • Content addressing
   • Cache invalidation

2. Security

   • Password hashing
   • Digital signatures
   • Token generation
   • Message authentication

3. Data Encoding

   • API data transfer
   • URL-safe data
   • Binary data representation
   • Configuration storage

Advanced Topics

1. Custom Hash Functions

   • Implementing hash.Hash interface
   • Custom HMAC implementations
   • Performance optimization
   • Security considerations

2. Advanced Encoding

   • Custom encodings
   • Streaming encoders
   • Performance tuning
   • Error recovery

3. Security Considerations

   • Side-channel attacks
   • Timing attacks
   • Memory safety
   • Key management

Running the Program

go run main.go

The program demonstrates:

• Various hash functions
• HMAC operations
• Common hashing patterns
• Different encoding formats
• Error handling and validation

Further Reading

• crypto Package Documentation
• encoding Package Documentation
• HMAC: Keyed-Hashing for Message Authentication
• Base64 Encoding