Crypt32.dll Encryption Algorithm

Question

We are using Crypt32.dll for encryption and its functions

1. CryptProtectData: To encrypt sensitive data and
2. CryptUnprotectData: To decrypt previously encrypted data.

We are trying to search which encryption algorithm it is using but we are not able find out. can someone help us to understand which encryption algorithm these functions use to encrypt and decrypt data?

Answer 1

Hello，

Thank you for posting in the Microsoft Community forum.

According to my research, the CryptProtectData and CryptUnprotectData functions in the Crypt32.dll library use the Data Protection API (DPAPI) for encryption and decryption. DPAPI typically employs a session key derived from the user's logon credentials to perform the encryption.

By default, DPAPI uses the AES256 encryption algorithm in CBC mode, along with SHA512 for hashing and PBKDF2 as the password-based key derivation function. These algorithms and their key lengths can be configured from the registry, but the default settings provide robust security.

For more information, please refer to the following articles:

https://www.passcape.com/index.php?section=docsys&cmd=details&id=28

https://learn.microsoft.com/en-us/windows/win32/api/dpapi/nf-dpapi-cryptprotectdata

I hope this helps.

Best regards

Jacen

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