How Secure is ASP.NET Identity's Default Password Hasher?

In-depth analysis of ASP.NET Identity default password hasher

ASP.NET Identity's default password hasher implementation is designed to provide strong and secure password hashes, leveraging industry-standard key derivation functions (KDF) and randomly generated salts.

How it works

The

HashPassword method generates a hash using a KDF (specifically Rfc2898DeriveBytes) with a random salt. The salt value is stored as a prefix to the hash value, resulting in a unique hash value for each password.

During verification (VerifyHashedPassword), the salt value is extracted from the hashed password and used to rehash the provided password. If the result matches the original hash, the password is considered valid.

Safety Precautions

The salt value is stored as part of the hash value, eliminating the risk of static salt values. Additionally, the random nature of the salt ensures that rainbow tables or precomputed hashes cannot be used effectively to crack passwords.

The default password hasher uses a PBKDF2-based KDF and a high iteration count, making brute force attacks infeasible. The KDF implementation is designed to resist timing attacks, further enhancing security.

Considerations about the statelessness of salt values

While the default password hasher does not explicitly store the salt value in a separate location, it is embedded into the hashed password. This configuration ensures that the salt value can be used during password verification, which is critical for secure password comparison.

Key points

• The default password hasher uses KDF with a random salt, resulting in a unique and secure hash.
• The salt value is included in the hashed password to prevent static salt value vulnerabilities.
• High iteration count and PBKDF2-based KDF provide strong resistance to brute force attacks.
• The lack of explicit salt storage does not affect the security of password authentication.

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