Explaining PBES2 Encryption
PBES2 (Password-Based Encryption Scheme 2) is a standard encryption scheme defined in PKCS #5 v2.0 (RFC 8018), designed to securely encrypt data using a password instead of a cryptographic key.
How PBES2 Works:
PBES2 is a two-stage encryption scheme:
1. Key Derivation
- A password is transformed into a strong symmetric key using a Key Derivation Function (KDF) — usually PBKDF2.
- Inputs to PBKDF2 include:
- Password
- Salt (random bytes)
- Iteration count
- Hash function (e.g. SHA-256)
- Desired key length
2. Encryption
- The derived key is used with a symmetric encryption algorithm (e.g., AES in CBC mode).
- An Initialization Vector (IV) is also generated and used in the encryption step.
PBES2 Components:
| Component | Description |
|---|---|
| Password | User-provided secret |
| Salt | Random data added to prevent rainbow table attacks |
| Iteration Count | Slows down brute-force attempts |
| KDF | Typically PBKDF2 |
| Cipher | Usually AES-128 or AES-256 in CBC mode |
| IV | Ensures ciphertext uniqueness |
Output:
The final output usually includes:
- Encrypted data
- Salt
- IV
- PBKDF2 parameters
- Cipher algorithm used
These are often packaged in PKCS#8 (for private key encryption) or other standardized formats like CMS EncryptedData.
Use Cases:
- Encrypting private keys in PKCS#8
- Password-protecting data archives
- Securely storing secrets with a user password