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

// Copyright 2018 Parity Technologies (UK) Ltd.
//
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// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
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// Software is furnished to do so, subject to the following conditions:
//
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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use super::codec::StreamCipher;
use crypto::{aessafe, blockmodes::CtrModeX8};

#[derive(Clone, Copy)]
pub enum Cipher {
    Aes128,
    Aes256,
}

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,
        }
    }

    /// Returns the size of in bytes of the IV expected by the cipher.
    #[inline]
    pub fn iv_size(&self) -> usize {
        16      // CTR 128
    }
}

/// Returns your stream cipher depending on `Cipher`.
#[inline]
pub fn ctr(key_size: Cipher, key: &[u8], iv: &[u8]) -> StreamCipher {
    match key_size {
        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))
        },
    }
}