HKDF Calculator

Generate secure cryptographic keys using HKDF (HMAC-based Key Derivation Function) with customizable parameters

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About This Tool

This HKDF online tool implements the HMAC-based Key Derivation Function (HKDF) as defined in RFC 5869. It allows you to derive cryptographically strong keys from input key material using a hash function (SHA-256, SHA-384, or SHA-512), optional salt, and context-specific information. The tool performs all calculations client-side in your browser using the Web Crypto API, ensuring your sensitive key material never leaves your device. HKDF is widely used in security protocols like TLS, Signal, and WireGuard for key derivation.

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How to Use

Enter your key material (input key) in the text area or upload a file
Optionally provide salt for additional entropy (recommended for security)
Add context-specific information (info parameter) to bind the derived key to the application context
Select the desired hash algorithm (SHA-256, SHA-384, or SHA-
Specify the output key length in bytes (1-8192 bytes)
Click 'Derive Key' to generate the HKDF-derived key
View the result in hexadecimal format, which you can copy for use in your applications

Frequently Asked Questions

Find Quick Answers

What is HKDF and when should I use it?

HKDF (HMAC-based Key Derivation Function) is a cryptographic algorithm defined in RFC 5869 for deriving secure keys from input key material. Use it when you need to generate cryptographic keys for encryption, authentication, or key agreement protocols from potentially weak or non-uniform input key material.

Is my key material secure when using this tool?

Yes, all calculations are performed entirely client-side in your browser using the Web Crypto API. Your key material, salt, and info parameters never leave your device or get transmitted to any server.

What's the purpose of the salt parameter?

Salt adds additional entropy to the key derivation process, making the derived key more secure against dictionary attacks. While optional, using a cryptographically random salt is recommended for security-critical applications.

What hash algorithms are supported?

The tool supports SHA-256 (256-bit output), SHA-384 (384-bit output), and SHA-512 (512-bit output). SHA-256 is the most commonly used and provides a good balance of security and performance.

What is the maximum output key length?

The tool supports output keys from 1 to 8192 bytes (65,536 bits). For most applications, 32 bytes (256 bits) is sufficient for AES-256 keys.

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