What is a HMAC-Secret in WebAuthn?

A HMAC-Secret is a cryptographic technique combining a message, a secret key, and a hash function to ensure data integrity and prevent unauthorized modifications. Components of HMAC-Secret:

• Message: Data being authenticated.
• Secret keys: Unique values known only to authorized parties.
• Cryptographic hash function: Transforms the input data into a fixed-size string of characters. HMAC-Secrets are used symmetrically, meaning the same secret key is employed for both generating and verifying the authentication code.

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• Security: Provides a strong layer of defense against data tampering and replay attacks.
• Integration: Widely supported across programming languages, facilitating easy adoption.
• Authentication: Plays a vital role in passkey-based and WebAuthn authentication methods.

• Key Management: Requires secure handling and storage of secret keys.
• Attack Limitations: While HMAC detects tampering, it cannot prevent all attack types.

• Passkeys, an advancement in the field of authentication, leverage the principles of HMAC-Secrets to establish secure, phishing-resistant authentication for users.

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• HMAC-Secret enhances WebAuthn and Passkeys by providing a method to verify data integrity and authenticity.

• Yes, HMAC-Secrets can be integrated with various authentication systems, including those based on WebAuthn and Passkeys, due to their wide support and flexible implementation.

• The main benefits include enhanced data security, compliance with regulatory standards, and ease of integration into existing systems.

• No, HMAC does not provide confidentiality. It ensures data integrity and authenticates the data source but does not encrypt the data to keep its contents secret. Confidentiality requires encryption, which can be used in conjunction with HMAC for a comprehensive security approach.