rust-libp2p/protocols/secio/src/stream_cipher.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
//
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use super::codec::StreamCipher;
use crypto::{aessafe, blockmodes::CtrModeX8, symmetriccipher::SynchronousStreamCipher};

/// Possible encryption ciphers.
#[derive(Clone, Copy, Debug)]
pub enum Cipher {
    Aes128,
    Aes256,
    Null
}

impl Cipher {
    /// Returns the size of in bytes of the key expected by the cipher.
    pub fn key_size(&self) -> usize {
        match *self {
            Cipher::Aes128 => 16,
            Cipher::Aes256 => 32,
            Cipher::Null => 0
        }
    }

    /// Returns the size of in bytes of the IV expected by the cipher.
    #[inline]
    pub fn iv_size(&self) -> usize {
        match self {
            Cipher::Aes128 | Cipher::Aes256 => 16,
            Cipher::Null => 0
        }
    }
}

/// A no-op cipher which does not encrypt or decrypt at all.
/// Obviously only useful for debugging purposes.
#[derive(Clone, Copy, Debug)]
pub struct NullCipher;

impl SynchronousStreamCipher for NullCipher {
    fn process(&mut self, input: &[u8], output: &mut [u8]) {
        output.copy_from_slice(input)
    }
}

/// Returns your stream cipher depending on `Cipher`.
#[inline]
pub fn ctr(c: Cipher, key: &[u8], iv: &[u8]) -> StreamCipher {
    match c {
        Cipher::Aes128 => {
            let aes_dec = aessafe::AesSafe128EncryptorX8::new(key);
            Box::new(CtrModeX8::new(aes_dec, iv))
        },
        Cipher::Aes256 => {
            let aes_dec = aessafe::AesSafe256EncryptorX8::new(key);
            Box::new(CtrModeX8::new(aes_dec, iv))
        },
        Cipher::Null => Box::new(NullCipher)
    }
}