HMAC Generator

Generate Hash-based Message Authentication Codes (HMAC) for message authentication and integrity verification.

Input Data

Secret Key

The secret key is used to authenticate the message. Keep it secure and share it only with authorized parties.

HMAC Settings

HMAC Output

HMAC output will appear here

About HMAC (Hash-based Message Authentication Code)

What is HMAC?

HMAC (Hash-based Message Authentication Code) is a cryptographic mechanism that provides both data integrity and authenticity verification. It combines a cryptographic hash function with a secret key to produce a unique authentication code.

Key Features:

  • Message Authentication: Verifies message sender
  • Data Integrity: Detects unauthorized changes
  • Non-repudiation: Prevents denial of message origin
  • Keyed Security: Requires secret key knowledge

How HMAC Works

HMAC uses a two-step process: it first applies the hash function to a combination of the secret key and message, then applies the hash function again to create the final authentication code.

HMAC Process:

  1. Prepare the secret key (pad or hash if needed)
  2. XOR key with inner padding constant
  3. Append message to padded key
  4. Hash the concatenated result
  5. XOR original key with outer padding
  6. Append previous hash result
  7. Hash again to produce final HMAC

Security Benefits

🛡️ Cryptographic Strength:

HMAC provides proven security based on the underlying hash function's cryptographic properties, making it resistant to various attack vectors.

  • Immune to length extension attacks
  • Resistant to collision attacks on hash function
  • Provides computational security guarantees
  • Standardized in RFC 2104 and FIPS 198-1

HMAC's security depends on the strength of the underlying hash function and the secrecy of the key, making it suitable for high-security applications.

Hash Algorithm Comparison

HMAC-SHA256:

Recommended for most applications. Excellent security and performance balance.

HMAC-SHA512:

Higher security for sensitive applications requiring maximum protection.

HMAC-SHA1:

Legacy algorithm. Consider upgrading to SHA-256 or higher.

HMAC-MD5:

Deprecated for security applications. Use only for compatibility.

Common Use Cases

  • API Authentication: Verify API requests and prevent tampering
  • Data Integrity: Ensure data hasn't been modified in transit
  • Digital Signatures: Create lightweight message authentication
  • Secure Protocols: Used in TLS, IPSec, and SSH protocols
  • Password Storage: Secure password verification systems
  • Blockchain: Transaction validation and block integrity

Best Practices

Implementation Guidelines:

  • Use cryptographically strong random keys (minimum 32 bytes)
  • Keep secret keys secure and rotate them regularly
  • Use SHA-256 or SHA-512 for new implementations
  • Implement constant-time comparison for HMAC verification
  • Never reuse keys across different applications
  • Include timestamp or nonce to prevent replay attacks

HMAC vs Other Methods

HMAC vs Simple Hash:

HMAC provides authentication; simple hashes only provide integrity.

HMAC vs Digital Signatures:

HMAC is faster and uses symmetric keys; digital signatures use asymmetric keys.

HMAC vs MAC:

HMAC is a specific type of MAC based on hash functions.

Output Formats

Hexadecimal:

Human-readable format, commonly used in debugging and documentation.

Base64:

Compact format suitable for transmission over text-based protocols.

Binary:

Raw binary format for direct use in binary protocols and systems.