//! Implementation for Counter Galois Onion (CGO) relay cell encryption

//!

//! CGO is an improved approach for encrypting relay cells, with better support

//! for tagging resistance, better forward secrecy, and other improvements.

//! It is described in [a paper][CGO] by Degabriele, Melloni, Münch, and Stam,

//! and specified in [proposal 359].

//!

//! CGO is based on a construction called "UIV+",

//! which provides the "robust pseudorandom permutation" security definition.

//! Notably, _encryption_ with UIV+ is non-malleable (and hence tagging resistant),

//! whereas _decryption_ with UIV+ is malleable (and hence not tagging resistant).

//!

//! [CGO]: https://eprint.iacr.org/2025/583

//! [proposal 359]: https://spec.torproject.org/proposals/359-cgo-redux.html

//

// Implementation note: For naming, I'm trying to use the symbols from the paper

// and the spec (which should be the same) wherever possible.

#![allow(dead_code)] // TODO CGO: Remove this once we actually use CGO encryption.

use aes::{Aes128, Aes128Dec, Aes128Enc, Aes256, Aes256Dec, Aes256Enc};

use cipher::{BlockCipher, BlockDecrypt, BlockEncrypt, BlockSizeUser, StreamCipher as _};

use digest::KeyInit;

use polyval::{Polyval, universal_hash::UniversalHash};

use tor_cell::{

    chancell::{CELL_DATA_LEN, ChanCmd},

    relaycell::msg::SendmeTag,

};

use tor_error::internal;

use zeroize::Zeroizing;

use super::{CryptInit, RelayCellBody};

use crate::{client::circuit::CircuitBinding, util::ct};

/// Size of CGO tag, in bytes.

const CGO_TAG_LEN: usize = 16;

/// Size of CGO payload, in bytes.

const CGO_PAYLOAD_LEN: usize = CELL_DATA_LEN - CGO_TAG_LEN;

/// Size of CGO additional data, in bytes.

///

/// This is used to encode whether the cell command is `RELAY`` or `RELAY_EARLY`.

const CGO_AD_LEN: usize = 16;

/// Size of the "H" tweak passed to the UIV+ construction.

const HLEN_UIV: usize = CGO_TAG_LEN + CGO_AD_LEN;

/// Block length.

/// Used by various types.

const BLK_LEN: usize = 16;

/// Block length as a typenum; used to parameterize some types

/// that use ArrayLen.

type BlockLen = typenum::U16;

/// A single block.  Used as input to various functions.

type Block = [u8; BLK_LEN];

/// Helper trait to define the features we need from a block cipher,

/// and make our "where" declarations smaller.

///

/// Not sealed because it is never used outside of this crate.

#[cfg_attr(feature = "bench", visibility::make(pub))]

pub(crate) trait BlkCipher:

    BlockCipher + KeyInit + BlockSizeUser<BlockSize = BlockLen> + Clone

{

    /// Length of the key used by this block cipher.

    const KEY_LEN: usize;

}

/// Helper trait to define the features we need from a block cipher,

/// and make our "where" declarations smaller.

///

/// Not sealed because it is never used outside of this crate.

#[cfg_attr(feature = "bench", visibility::make(pub))]

pub(crate) trait BlkCipherEnc: BlkCipher + BlockEncrypt {}

/// Helper trait to define the features we need from a block cipher,

/// and make our "where" declarations smaller.

///

/// Not sealed because it is never used outside of this crate.

#[cfg_attr(feature = "bench", visibility::make(pub))]

pub(crate) trait BlkCipherDec: BlkCipher + BlockDecrypt {}

impl BlkCipher for Aes128 {

    const KEY_LEN: usize = 16;

}

impl BlkCipherEnc for Aes128 {}

impl BlkCipherDec for Aes128 {}

impl BlkCipher for Aes128Enc {

    const KEY_LEN: usize = 16;

}

impl BlkCipherEnc for Aes128Enc {}

impl BlkCipher for Aes128Dec {

    const KEY_LEN: usize = 16;

}

impl BlkCipherDec for Aes128Dec {}

impl BlkCipher for Aes256 {

    const KEY_LEN: usize = 32;

}

impl BlkCipherEnc for Aes256 {}

impl BlkCipherDec for Aes256 {}

impl BlkCipher for Aes256Enc {

    const KEY_LEN: usize = 32;

}

impl BlkCipherEnc for Aes256Enc {}

impl BlkCipher for Aes256Dec {

    const KEY_LEN: usize = 32;

}

impl BlkCipherDec for Aes256Dec {}

/// Define a tweakable block cipher.

mod et {

    use super::*;

    /// Type of the tweak accepted by the tweakable block cipher.

    ///

    /// (This might seem like a weird way to express `&[u8; TLEN_ET]`,

    /// but it _is_ the way that the UIV construction will provide the tweak.)

    pub(super) type EtTweak<'a> = (&'a [u8; CGO_TAG_LEN], u8, &'a [u8; CGO_PAYLOAD_LEN]);

    /// Total length of EtTweak fields.

    pub(super) const TLEN_ET: usize = CGO_TAG_LEN + 1 + CGO_PAYLOAD_LEN;

    /// Implementation for an LRW2 tweakable block cipher,

    /// with block length of [`BLK_LEN`],

    /// and specialized tweak of type [`EtTweak`].

    ///

    /// Corresponds to ET in the specification.

    #[derive(Clone)]

    pub(super) struct EtCipher<BC: BlkCipher> {

        /// Underlying block cipher

        kb: BC,

        /// Universal hash, initialized with the key KU.

        ku: Polyval,

    }

    impl<BC: BlkCipher> EtCipher<BC> {

        /// Helper: Given a tweak, compute the blinding value we will use

        /// for encrypting or decryption.

            // We want to compute the UH(KU, tweak.0 | tweak.1 | tweak.2).

            // This implementation is optimized to avoid excessive data copying.

    }

    impl<BC: BlkCipherEnc> EtCipher<BC> {

        /// Encrypt `block` in-place, using `tweak`.

            // ENC_ET((KB,KU), T, M) = UH(KU,T) ^ ENC_BC(KB, M ^ UH(KU,T))

    }

    impl<BC: BlkCipherDec> EtCipher<BC> {

        /// Decrypt `block` in-place, using `tweak`.

            // DEC_ET((KB,KU), T, M) = UH(KU,T) ^ DEC_BC(KB, M ^ UH(KU,T))

    }

    impl<BC: BlkCipher> CryptInit for EtCipher<BC> {

            // TODO PERF: Here and throughout, these initialize functions do more checking than we

            // necessarily need.  We should see if we can simplify them.

    }

}

/// Define a tweakable pseudorandom stream generator.

mod prf {

    use tor_error::internal;

    use super::*;

    /// The type used as a tweak for this PRF.

    type PrfTweak = [u8; 16];

    /// Length of the PRF's output when used with t=0.

    const PRF_N0_LEN: usize = CGO_PAYLOAD_LEN;

    /// Offset of the PRF's output when used with t=1.

    const PRF_N1_OFFSET: usize = 31 * 16;

    const _: () = assert!(PRF_N1_OFFSET >= PRF_N0_LEN);

    /// Pseudorandom function based on CTR128, Polyval, and an underlying block cipher.

    //

    // Definition: PRF((K, B), T, t) = CTR_{nt}(K, UH(B, T) + (t * C)).

    //   where t is 0 or 1 and C is 31.

    #[derive(Clone)]

    pub(super) struct Prf<BC: BlkCipherEnc> {

        /// The underlying block cipher, initialized with the key "K"

        k: BC,

        /// Thu underlying universal hash, initialized with the key "B"

        b: Polyval,

    }

    impl<BC: BlkCipherEnc> Prf<BC> {

        /// Helper: Return a stream cipher, initialized with an IV corresponding

        /// to `tweak` and an offset corresponding to `t`.

            use {

                cipher::{InnerIvInit as _, StreamCipherSeek as _},

                ctr::CtrCore,

            };

            );

        /// Apply the cipherstream from this Prf to `out`, with tweak parameter `tweak`

        /// and offset parameter `t=0`.

        /// Return a vector containing `n` bytes of this Prf, with tweak

        /// parameter `tweak` and offset parameter `t=1`.

    }

    impl<BC: BlkCipherEnc> CryptInit for Prf<BC> {

    }

}

/// Define the UIV+ tweakable wide-block cipher.

///

/// This construction is a "rugged pseudorandom permutation"; see above.

mod uiv {

    use super::*;

    /// Type of tweak used as input to the UIV encryption and decryption algorithms.

    pub(super) type UivTweak<'a> = (&'a [u8; BLK_LEN], u8);

    /// Keys for a UIV cipher.

    #[derive(Clone)]

    pub(super) struct Uiv<EtBC: BlkCipher, PrfBC: BlkCipherEnc> {

        /// Tweakable block cipher key; corresponds to J in the specification.

        j: et::EtCipher<EtBC>,

        /// PRF keys; corresponds to S in the specification.

        s: prf::Prf<PrfBC>,

        /// Testing only: a copy of our current key material.

        ///

        /// (Used because otherwise, we cannot extract keys from our components,

        /// but we _do_ need to test that our key update code works sensibly.)

        #[cfg(test)]

        pub(super) keys: Zeroizing<Vec<u8>>,

    }

    /// Helper: split a mutable cell body into the left-hand (tag) and

    /// right-hand (body) parts.

        //TODO PERF: Make sure that there is no actual checking done here!

    impl<EtBC: BlkCipherEnc, PrfBC: BlkCipherEnc> Uiv<EtBC, PrfBC> {

        /// Encrypt `cell_body`, using the provided `tweak`.

        ///

        /// Corresponds to `ENC_UIV.`

            // ENC_UIV((J,S), H, (X_L,X_R)):

            //     Y_L <-- ENC_ET(J, (H || X_R), X_L)

            //     Y_R <-- X_R ^ PRF_n0(S, Y_L, 0)

            //     return (Y_L, Y_R)

    }

    impl<EtBC: BlkCipherDec, PrfBC: BlkCipherEnc> Uiv<EtBC, PrfBC> {

        /// Decrypt `cell_body`, using the provided `tweak`.

        ///

        /// Corresponds to `DEC_UIV`.

            // DEC_UIV((J,S), H, (Y_L,Y_R)):

            //    X_R <-- Y_R xor PRF_n0(S, Y_L, 0)

            //    X_L <-- DEC_ET(J, (H || X_R), Y_L)

            //    return (X_L, X_R)

    }

    impl<EtBC: BlkCipher, PrfBC: BlkCipherEnc> Uiv<EtBC, PrfBC> {

        /// Modify this Uiv, and the provided nonce, so that its current state

        /// cannot be recovered.

        ///

        /// Corresponds to `UPDATE_UIV`

            // UPDATE_UIV((J,S), N):

            //     ((J',S'), N') = PRF_{n1}(S, N, 1)

            //     return ((J', S'), N')

            // TODO PERF: We could allocate significantly less here, by using

            // reinitialize functions, and by not actually expanding the key

            // stream.

            #[cfg(test)]

        /// Helper: divide seed into J, S, and N.

    }

    impl<EtBC: BlkCipher, PrfBC: BlkCipherEnc> CryptInit for Uiv<EtBC, PrfBC> {

            #[cfg(test)]

            Ok(Self {

                #[cfg(test)]

            })

    }

}

/// Xor all bytes from `input` into `output`.

/// Helper: return the first `BLK_LEN` bytes of a slice as an array.

///

/// TODO PERF: look for other ways to express this, and/or make sure that it

/// compiles down to something minimal.

#[inline]

/// State of a single direction of a CGO layer, at the client or at a relay.

#[derive(Clone)]

struct CryptState<EtBC: BlkCipher, PrfBC: BlkCipherEnc> {

    /// The current key "K" for this direction.

    uiv: uiv::Uiv<EtBC, PrfBC>,

    /// The current nonce value "N" for this direction.

    nonce: Zeroizing<[u8; BLK_LEN]>,

    /// The current tag value "T'" for this direction.

    tag: Zeroizing<[u8; BLK_LEN]>,

}

impl<EtBC: BlkCipher, PrfBC: BlkCipherEnc> CryptInit for CryptState<EtBC, PrfBC> {

    /// Construct this state from a seed of the appropriate length.

        Ok(Self {

        })

}

/// An instance of CGO used for outbound client encryption.

#[cfg_attr(feature = "bench", visibility::make(pub))]

#[derive(Clone, derive_more::From)]

pub(crate) struct ClientOutbound<EtBC, PrfBC>(CryptState<EtBC, PrfBC>)

where

    EtBC: BlkCipherDec,

    PrfBC: BlkCipherEnc;

impl<EtBC, PrfBC> super::OutboundClientLayer for ClientOutbound<EtBC, PrfBC>

where

    EtBC: BlkCipherDec,

    PrfBC: BlkCipherEnc,

{

        // TODO PERF: consider swap here.

        // Note use of decrypt here: Client operations always use _decrypt_,

        // and relay operations always use _encrypt_.

}

/// An instance of CGO used for inbound client encryption.

#[cfg_attr(feature = "bench", visibility::make(pub))]

#[derive(Clone, derive_more::From)]

pub(crate) struct ClientInbound<EtBC, PrfBC>(CryptState<EtBC, PrfBC>)

where

    EtBC: BlkCipherDec,

    PrfBC: BlkCipherEnc;

impl<EtBC, PrfBC> super::InboundClientLayer for ClientInbound<EtBC, PrfBC>

where

    EtBC: BlkCipherDec,

    PrfBC: BlkCipherEnc,

{

        // let t_orig_orig = t_orig;

        // Note use of decrypt here: Client operations always use _decrypt_,

        // and relay operations always use _encrypt_.

            // assert_eq!(self.0.tag[..BLK_LEN], t_orig_orig[..]);

        } else {

        }

}

/// An instance of CGO used for outbound (away from the client) relay encryption.

#[cfg_attr(feature = "bench", visibility::make(pub))]

#[derive(Clone, derive_more::From)]

pub(crate) struct RelayOutbound<EtBC, PrfBC>(CryptState<EtBC, PrfBC>)

where

    EtBC: BlkCipherEnc,

    PrfBC: BlkCipherEnc;

impl<EtBC, PrfBC> super::OutboundRelayLayer for RelayOutbound<EtBC, PrfBC>

where

    EtBC: BlkCipherEnc,

    PrfBC: BlkCipherEnc,

{

        // Note use of encrypt here: Client operations always use _decrypt_,

        // and relay operations always use _encrypt_.

        } else {

        }

}

/// An instance of CGO used for inbound (towards the client) relay encryption.

#[cfg_attr(feature = "bench", visibility::make(pub))]

#[derive(Clone, derive_more::From)]

pub(crate) struct RelayInbound<EtBC, PrfBC>(CryptState<EtBC, PrfBC>)

where

    EtBC: BlkCipherEnc,

    PrfBC: BlkCipherEnc;

impl<EtBC, PrfBC> super::InboundRelayLayer for RelayInbound<EtBC, PrfBC>

where

    EtBC: BlkCipherEnc,

    PrfBC: BlkCipherEnc,

{

        // assert_eq!(self.0.tag[..BLK_LEN], cell.0[0..BLK_LEN]);

        // Note use of encrypt here: Client operations always use _decrypt_,

        // and relay operations always use _encrypt_.

}

/// A set of cryptographic information as shared by the client and a single relay,

/// and

#[cfg_attr(feature = "bench", visibility::make(pub))]

#[derive(Clone)]

pub(crate) struct CryptStatePair<EtBC, PrfBC>

where

    EtBC: BlkCipher,

    PrfBC: BlkCipherEnc,

{

    /// State for the outbound direction (away from client)

    outbound: CryptState<EtBC, PrfBC>,

    /// State for the inbound direction (towards client)

    inbound: CryptState<EtBC, PrfBC>,

    /// Circuit binding information.

    binding: CircuitBinding,

}

impl<EtBC, PrfBC> CryptInit for CryptStatePair<EtBC, PrfBC>

where

    EtBC: BlkCipher,

    PrfBC: BlkCipherEnc,

{

        const {

            // can't use assert_eq!() in const

            assert!(EtBC::KEY_LEN == PrfBC::KEY_LEN);

        }

        Ok(Self {

        })

}

impl<EtBC, PrfBC> super::ClientLayer<ClientOutbound<EtBC, PrfBC>, ClientInbound<EtBC, PrfBC>>

    for CryptStatePair<EtBC, PrfBC>

where

    EtBC: BlkCipherDec,

    PrfBC: BlkCipherEnc,

{

}

impl<EtBC, PrfBC> super::RelayLayer<RelayOutbound<EtBC, PrfBC>, RelayInbound<EtBC, PrfBC>>

    for CryptStatePair<EtBC, PrfBC>

where

    EtBC: BlkCipherEnc,

    PrfBC: BlkCipherEnc,

{

}

/// Benchmark utilities for the `cgo` module.

#[cfg(feature = "bench")]

pub mod bench_utils {

    pub use super::ClientInbound;

    pub use super::ClientOutbound;

    pub use super::CryptStatePair;

    pub use super::RelayInbound;

    pub use super::RelayOutbound;

    /// The throughput for a relay cell in bytes with the CGO scheme.

    pub const CGO_THROUGHPUT: u64 = 488;

}

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use crate::crypto::cell::{

        InboundRelayLayer, OutboundClientCrypt, OutboundClientLayer, OutboundRelayLayer,

    };

    use super::*;

    use hex_literal::hex;

    use rand::Rng as _;

    use tor_basic_utils::test_rng::testing_rng;

    #[test]

    fn testvec_xor() {

        let mut b: [u8; 20] = *b"turning and turning ";

        let s = b"in the widening gyre";

        xor_into(&mut b, s);

        assert_eq!(b[..], hex!("1d1b521a010b4757080a014e1d1b154e0e171545"));

    }

    #[test]

    fn testvec_polyval() {

        use polyval::Polyval;

        use polyval::universal_hash::UniversalHash;

        // Test vectors from RFC8452 worked example in appendix A.

        let h = hex!("25629347589242761d31f826ba4b757b");

        let x_1 = hex!("4f4f95668c83dfb6401762bb2d01a262");

        let x_2 = hex!("d1a24ddd2721d006bbe45f20d3c9f362");

        let mut hash = Polyval::new(&h.into());

        hash.update(&[x_1.into(), x_2.into()]);

        let result: [u8; 16] = hash.finalize().into();

        assert_eq!(result, hex!("f7a3b47b846119fae5b7866cf5e5b77e"));

    }

    // These True/False constants are here to make our test data parse without changes.

    #[allow(non_upper_case_globals)]

    const False: bool = false;

    #[allow(non_upper_case_globals)]

    const True: bool = true;

    include!("../../../testdata/cgo_et.rs");

    include!("../../../testdata/cgo_prf.rs");

    include!("../../../testdata/cgo_uiv.rs");

    include!("../../../testdata/cgo_relay.rs");

    include!("../../../testdata/cgo_client.rs");

    /// Decode s as a N-byte hex string, or panic.

    fn unhex<const N: usize>(s: &str) -> [u8; N] {

        hex::decode(s).unwrap().try_into().unwrap()

    }

    #[test]

    fn testvec_et() {

        for (encrypt, keys, tweak, input, expect_output) in ET_TEST_VECTORS {

            let keys: [u8; 32] = unhex(keys);

            let tweak: [u8; et::TLEN_ET] = unhex(tweak);

            let mut block: [u8; 16] = unhex(input);

            let expect_output: [u8; 16] = unhex(expect_output);

            let et: et::EtCipher<Aes128> = et::EtCipher::initialize(&keys).unwrap();

            let tweak = (

                tweak[0..16].try_into().unwrap(),

                tweak[16],

                &tweak[17..].try_into().unwrap(),

            );

            if *encrypt {

                et.encrypt(tweak, &mut block);

            } else {

                et.decrypt(tweak, &mut block);

            }

            assert_eq!(block, expect_output);

        }

    }

    #[test]

    fn testvec_prf() {

        for (keys, offset, tweak, expect_output) in PRF_TEST_VECTORS {

            let keys: [u8; 32] = unhex(keys);

            assert!([0, 1].contains(offset));

            let tweak: [u8; 16] = unhex(tweak);

            let expect_output = hex::decode(expect_output).unwrap();

            let prf: prf::Prf<Aes128> = prf::Prf::initialize(&keys).unwrap();

            if *offset == 0 {

                assert_eq!(expect_output.len(), CGO_PAYLOAD_LEN);

                let mut data = [0_u8; CGO_PAYLOAD_LEN];

                prf.xor_n0_stream(&tweak, &mut data);

                assert_eq!(expect_output[..], data[..]);

            } else {

                let data = prf.get_n1_stream(&tweak, expect_output.len());

                assert_eq!(expect_output[..], data[..]);

            }

        }

    }

    #[test]

    fn testvec_uiv() {

        for (encrypt, keys, tweak, left, right, (expect_left, expect_right)) in UIV_TEST_VECTORS {

            let keys: [u8; 64] = unhex(keys);

            let tweak: [u8; 17] = unhex(tweak);

            let mut cell: [u8; 509] = unhex(&format!("{left}{right}"));

            let expected: [u8; 509] = unhex(&format!("{expect_left}{expect_right}"));

            let uiv: uiv::Uiv<Aes128, Aes128> = uiv::Uiv::initialize(&keys).unwrap();

            let htweak = (tweak[0..16].try_into().unwrap(), tweak[16]);

            if *encrypt {

                uiv.encrypt(htweak, &mut cell);

            } else {

                uiv.decrypt(htweak, &mut cell);

            }

            assert_eq!(cell, expected);

        }

    }

    #[test]

    fn testvec_uiv_update() {

        let mut rng = testing_rng();

        for (keys, nonce, (expect_keys, expect_nonce)) in UIV_UPDATE_TEST_VECTORS {

            let keys: [u8; 64] = unhex(keys);

            let mut nonce: [u8; 16] = unhex(nonce);

            let mut uiv: uiv::Uiv<Aes128, Aes128> = uiv::Uiv::initialize(&keys).unwrap();

            let expect_keys: [u8; 64] = unhex(expect_keys);

            let expect_nonce: [u8; 16] = unhex(expect_nonce);

            uiv.update(&mut nonce);

            assert_eq!(&nonce, &expect_nonce);

            assert_eq!(&uiv.keys[..], &expect_keys[..]);

            // Make sure that we can get the same results when we initialize a new UIV with the keys

            // allegedly used to reinitialize this one.

            let uiv2: uiv::Uiv<Aes128, Aes128> = uiv::Uiv::initialize(&uiv.keys[..]).unwrap();

            let tweak: [u8; 16] = rng.random();

            let cmd = rng.random();

            let mut msg1: [u8; CELL_DATA_LEN] = rng.random();

            let mut msg2 = msg1.clone();

            uiv.encrypt((&tweak, cmd), &mut msg1);

            uiv2.encrypt((&tweak, cmd), &mut msg2);

        }

    }

    #[test]

    fn testvec_cgo_relay() {

        for (inbound, (k, n, tprime), ad, t, c, output) in CGO_RELAY_TEST_VECTORS {

            let k_n: [u8; 80] = unhex(&format!("{k}{n}"));

            let tprime: [u8; 16] = unhex(tprime);

            let ad: [u8; 1] = unhex(ad);

            let msg: [u8; CELL_DATA_LEN] = unhex(&format!("{t}{c}"));

            let mut msg = RelayCellBody(Box::new(msg));

            let mut state = CryptState::<Aes128, Aes128>::initialize(&k_n).unwrap();

            *state.tag = tprime;

            let state = if *inbound {

                let mut s = RelayInbound::from(state);

                s.encrypt_inbound(ad[0].into(), &mut msg);

                s.0

            } else {

                let mut s = RelayOutbound::from(state);

                s.decrypt_outbound(ad[0].into(), &mut msg);

                s.0

            };

            // expected values

            let ((ex_k, ex_n, ex_tprime), (ex_t, ex_c)) = output;

            let ex_msg: [u8; CELL_DATA_LEN] = unhex(&format!("{ex_t}{ex_c}"));

            let ex_k: [u8; 64] = unhex(ex_k);

            let ex_n: [u8; 16] = unhex(ex_n);

            let ex_tprime: [u8; 16] = unhex(ex_tprime);

            assert_eq!(&ex_msg[..], &msg.0[..]);

            assert_eq!(&state.uiv.keys[..], &ex_k[..]);

            assert_eq!(&state.nonce[..], &ex_n[..]);

            assert_eq!(&state.tag[..], &ex_tprime[..]);

        }

    }

    #[test]

    fn testvec_cgo_relay_originate() {

        for ((k, n, tprime), ad, m, output) in CGO_RELAY_ORIGINATE_TEST_VECTORS {

            let k_n: [u8; 80] = unhex(&format!("{k}{n}"));

            let tprime: [u8; 16] = unhex(tprime);

            let ad: [u8; 1] = unhex(ad);

            let msg_body: [u8; CGO_PAYLOAD_LEN] = unhex(m);

            let mut msg = [0_u8; CELL_DATA_LEN];

            msg[16..].copy_from_slice(&msg_body[..]);

            let mut msg = RelayCellBody(Box::new(msg));

            let mut state = CryptState::<Aes128, Aes128>::initialize(&k_n).unwrap();

            *state.tag = tprime;

            let mut state = RelayInbound::from(state);

            state.originate(ad[0].into(), &mut msg);

            let state = state.0;

            let ((ex_k, ex_n, ex_tprime), (ex_t, ex_c)) = output;

            let ex_msg: [u8; CELL_DATA_LEN] = unhex(&format!("{ex_t}{ex_c}"));

            let ex_k: [u8; 64] = unhex(ex_k);

            let ex_n: [u8; 16] = unhex(ex_n);

            let ex_tprime: [u8; 16] = unhex(ex_tprime);

            assert_eq!(&ex_msg[..], &msg.0[..]);

            assert_eq!(&state.uiv.keys[..], &ex_k[..]);

            assert_eq!(&state.nonce[..], &ex_n[..]);

            assert_eq!(&state.tag[..], &ex_tprime[..]);

        }

    }

    #[test]

    fn testvec_cgo_client_originate() {

        for (ss, hop, ad, m, output) in CGO_CLIENT_ORIGINATE_TEST_VECTORS {

            assert!(*hop > 0); // the test vectors are 1-indexed.

            let mut client = OutboundClientCrypt::new();

            let mut individual_layers = Vec::new();

            for (k, n, tprime) in ss {

                let k_n: [u8; 80] = unhex(&format!("{k}{n}"));

                let tprime: [u8; 16] = unhex(tprime);

                let mut state = CryptState::<Aes128, Aes128>::initialize(&k_n).unwrap();

                *state.tag = tprime;

                client.add_layer(Box::new(ClientOutbound::from(state.clone())));

                individual_layers.push(ClientOutbound::from(state));

            }

            let ad: [u8; 1] = unhex(ad);

            let msg_body: [u8; CGO_PAYLOAD_LEN] = unhex(m);

            let mut msg = [0_u8; CELL_DATA_LEN];

            msg[16..].copy_from_slice(&msg_body[..]);

            let mut msg = RelayCellBody(Box::new(msg));

            let mut msg2 = msg.clone();

            // Encrypt using the OutboundClientCrypt object...

            client

                .encrypt(ad[0].into(), &mut msg, (*hop - 1).into())

                .unwrap();

            // And a second time manually, using individual_layers.

            //

            // (We do this so we can actually inspect that their internal state matches the test vectors.)

            {

                let hop_idx = usize::from(*hop) - 1;

                individual_layers[hop_idx].originate_for(ad[0].into(), &mut msg2);

                for idx in (0..hop_idx).rev() {

                    individual_layers[idx].encrypt_outbound(ad[0].into(), &mut msg2);

                }

            }

            assert_eq!(&msg.0[..], &msg2.0[..]);

            let (ex_ss, (ex_t, ex_c)) = output;

            let ex_msg: [u8; CELL_DATA_LEN] = unhex(&format!("{ex_t}{ex_c}"));

            assert_eq!(&ex_msg[..], &msg.0[..]);

            for (layer, (ex_k, ex_n, ex_tprime)) in individual_layers.iter().zip(ex_ss.iter()) {

                let state = &layer.0;

                let ex_k: [u8; 64] = unhex(ex_k);

                let ex_n: [u8; 16] = unhex(ex_n);

                let ex_tprime: [u8; 16] = unhex(ex_tprime);

                assert_eq!(&state.uiv.keys[..], &ex_k[..]);

                assert_eq!(&state.nonce[..], &ex_n[..]);

                assert_eq!(&state.tag[..], &ex_tprime);

            }

        }

    }

}