Struct StateEncryption 

pub struct StateEncryption { /* private fields */ }

State encryption using ChaCha20-Poly1305 AEAD

Provides authenticated encryption for OAuth state parameters. Uses a fixed encryption key for the deployment lifetime. Each encryption uses a random nonce for security.

Security Properties

• Confidentiality: State values are encrypted with ChaCha20
• Authenticity: Authentication tag prevents tampering detection
• Replay Prevention: Random nonce in each encryption
• Key Isolation: Separate from signing keys, used only for state

Implementations

impl StateEncryption

pub fn new(key_bytes: &[u8; 32]) -> Result<Self>

Create a new state encryption instance

Arguments

• key - 32-byte encryption key (must be cryptographically random)

Errors

Returns error if key is invalid

pub fn encrypt(&self, state: &str) -> Result<EncryptedState>

Encrypt a state value

Generates a random 96-bit nonce and encrypts the state using ChaCha20-Poly1305. The authentication tag is appended to the ciphertext.

Arguments

• state - The plaintext state value to encrypt

Returns

EncryptedState containing ciphertext and nonce

Errors

Returns error if encryption fails (should be rare)

pub fn decrypt(&self, encrypted: &EncryptedState) -> Result<String>

Decrypt and verify a state value

Uses the nonce from EncryptedState to decrypt the ciphertext. Authentication tag verification is automatic - tampering is detected.

Arguments

• encrypted - The encrypted state to decrypt

Returns

The decrypted plaintext state value

Errors

Returns error if:

• Authentication tag verification fails (tampering detected)
• Decryption fails
• Result is not valid UTF-8

pub fn encrypt_to_bytes(&self, state: &str) -> Result<Vec<u8>>

Encrypt state and serialize to bytes.

Errors

Returns AuthError::Internal if AEAD encryption fails (essentially never).

pub fn decrypt_from_bytes(&self, bytes: &[u8]) -> Result<String>

Decrypt state from serialized bytes.

Errors

Returns AuthError::InvalidState if bytes is too short, if AEAD authentication fails (tampered or wrong key), or if decrypted bytes are not valid UTF-8.