Struct AesOpeKey

pub(crate) struct AesOpeKey {
    key: Zeroizing<[u8; 32]>,
}

Key for a simple order-preserving encryption on the offset from the start of an SRV protocol run.

The algorithm here is chosen to be the same as used in the C tor implementation.

Fields

key: Zeroizing<[u8; 32]>

Implementations

impl AesOpeKey

pub fn from_secret(secret: &[u8]) -> AesOpeKey

Construct a new AesOpeKey from a given secret.

The secret should be unpredictable by an adversary.

pub fn encrypt(&self, offset: SrvPeriodOffset) -> u64

Encrypt offset to a 64-bit number.

(We do not implement a decryption operation.)

Limitations

Like all order-preserving encryption, this scheme leaks information by its nature. It also leaks more information than necessary: (the adversary can get a rough estimate for our input by dividing the output by 0x8001). The only security property that this algorithm tries to provide is that it prevents an adversary from inferring our clock skew.

This algorithm is also not very efficient in its implementation. We expect that the result will become unacceptable if the time period is ever larger than a few days.

Trait Implementations

impl Clone for AesOpeKey

fn clone(&self) -> AesOpeKey

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AesOpeKey

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.