add Ed25519 and Ed25519Extended asymmetric keys

pallas-crypto/Cargo.toml

@@ -16,4 +16,10 @@ authors = [
 minicbor = { version = "0.12" }
 hex = "0.4"
 cryptoxide = { version = "0.3.6" }
+thiserror = "1.0"
+rand_core = "0.6"
 
+[dev-dependencies]
+quickcheck = "1.0"
+quickcheck_macros = "1.0"
+rand = "0.8"

pallas-crypto/README.md

@@ -4,8 +4,8 @@ Crate with all the cryptographic material to support Cardano protocol:
 
 - [x] Blake2b 256
 - [x] Blake2b 224
-- [ ] Ed25519 asymmetric key pair and ECDSA
-- [ ] Ed25519 Extended asymmetric key pair
+- [x] Ed25519 asymmetric key pair and EdDSA
+- [x] Ed25519 Extended asymmetric key pair
 - [ ] Bip32-Ed25519 key derivation
 - [ ] BIP39 mnemonics
 - [ ] VRF

pallas-crypto/src/key/ed25519.rs

@@ -0,0 +1,528 @@
+//! Ed25519 and Ed25519Extended Asymmetric Keys
+//!
+//! In this module we have both [`SecretKey`] which is a normal Ed25519
+//! asymmetric key and [`SecretKeyExtended`] asymmetric key.
+//! They can both be used to generate [`Signature`] and submit valid
+//! transactions.
+//!
+//! However, only the [`SecretKeyExtended`] can be used for HD derivation
+//! (using [ed25519_bip32] or otherwise).
+//!
+
+use crate::memsec::Scrubbed as _;
+use cryptoxide::ed25519::{
+    self, PRIVATE_KEY_LENGTH, PUBLIC_KEY_LENGTH, SEED_LENGTH, SIGNATURE_LENGTH,
+};
+use rand_core::{CryptoRng, RngCore};
+use std::{any::type_name, convert::TryFrom, fmt, str::FromStr};
+use thiserror::Error;
+
+/// Ed25519 Secret Key
+///
+#[derive(Clone)]
+pub struct SecretKey([u8; Self::SIZE]);
+
+/// Ed25519 Extended Secret Key
+///
+/// unlike [`SecretKey`], an extended key can be derived see [`pallas_crypto::derivation`]
+#[derive(Clone)]
+pub struct SecretKeyExtended([u8; Self::SIZE]);
+
+/// Ed25519 Public Key. Can be used to verify a [`Signature`]. A [`PublicKey`]
+/// is associated to a [`SecretKey`]
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct PublicKey([u8; Self::SIZE]);
+
+/// Ed25519 Signature. Is created by a [`SecretKey`] and is verified
+/// with a [`PublicKey`].
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Signature([u8; Self::SIZE]);
+
+/// Error type used when retrieving a [`PublicKey`] via the [`TryFrom`]
+/// trait.
+#[derive(Debug, Error)]
+pub enum TryFromPublicKeyError {
+    #[error("Invalid size, expecting {}", PublicKey::SIZE)]
+    InvalidSize,
+}
+
+/// Error type used when retrieving a [`Signature`] via the [`TryFrom`]
+/// trait.
+#[derive(Debug, Error)]
+pub enum TryFromSignatureError {
+    #[error("Invalid size, expecting {}", Signature::SIZE)]
+    InvalidSize,
+}
+
+macro_rules! impl_size_zero {
+    ($Type:ty, $Size:expr) => {
+        impl $Type {
+            /// This is the size of the type in bytes.
+            pub const SIZE: usize = $Size;
+
+            /// create a zero object. This is not a _"valid"_ one. It is
+            /// used to initialize a ready to use data structure in this module.
+            #[inline]
+            fn zero() -> Self {
+                Self([0; Self::SIZE])
+            }
+        }
+    };
+}
+
+impl_size_zero!(SecretKey, SEED_LENGTH);
+impl_size_zero!(SecretKeyExtended, PRIVATE_KEY_LENGTH);
+impl_size_zero!(PublicKey, PUBLIC_KEY_LENGTH);
+impl_size_zero!(Signature, SIGNATURE_LENGTH);
+
+impl SecretKey {
+    /// generate a new [`SecretKey`] with the given random number generator
+    ///
+    pub fn new<Rng>(mut rng: Rng) -> Self
+    where
+        Rng: RngCore + CryptoRng,
+    {
+        let mut s = Self::zero();
+        rng.fill_bytes(&mut s.0);
+        s
+    }
+
+    /// get the [`PublicKey`] associated to this key
+    ///
+    /// Unlike the [`SecretKey`], the [`PublicKey`] can be safely
+    /// publicly shared. The key can then be used to verify any
+    /// [`Signature`] generated with this [`SecretKey`] and the original
+    /// message.
+    pub fn public_key(&self) -> PublicKey {
+        let (mut sk, pk) = ed25519::keypair(&self.0);
+
+        // the `sk` is a private component, scrubbing it reduce the
+        // risk of an adversary accessing the memory remains of this
+        // value
+        sk.scrub();
+
+        PublicKey(pk)
+    }
+
+    /// create a [`Signature`] for the given message with this [`SecretKey`].
+    ///
+    /// The [`Signature`] can then be verified against the associated [`PublicKey`]
+    /// and the original message.
+    pub fn sign<T>(&self, msg: T) -> Signature
+    where
+        T: AsRef<[u8]>,
+    {
+        let (mut sk, _) = ed25519::keypair(&self.0);
+
+        let signature = ed25519::signature(msg.as_ref(), &sk);
+
+        // we don't need this signature component, make sure to scrub the
+        // content before releasing the results
+        sk.scrub();
+
+        Signature(signature)
+    }
+}
+
+impl SecretKeyExtended {
+    /// generate a new [`SecretKeyExtended`] with the given random number generator
+    ///
+    pub fn new<Rng>(mut rng: Rng) -> Self
+    where
+        Rng: RngCore + CryptoRng,
+    {
+        let mut s = Self::zero();
+        rng.fill_bytes(&mut s.0);
+
+        s.0[0] &= 0b1111_1000;
+        s.0[31] &= 0b0011_1111;
+        s.0[31] |= 0b0100_0000;
+
+        debug_assert!(
+            s.check_structure(),
+            "checking we properly set the bit tweaks for the extended Ed25519"
+        );
+
+        s
+    }
+
+    #[inline]
+    #[allow(clippy::verbose_bit_mask)]
+    fn check_structure(&self) -> bool {
+        (self.0[0] & 0b0000_0111) == 0
+            && (self.0[31] & 0b0100_0000) == 0b0100_0000
+            && (self.0[31] & 0b1000_0000) == 0
+    }
+
+    /// get the [`PublicKey`] associated to this key
+    ///
+    /// Unlike the [`SecretKeyExtended`], the [`PublicKey`] can be safely
+    /// publicly shared. The key can then be used to verify any
+    /// [`Signature`] generated with this [`SecretKeyExtended`] and the original
+    /// message.
+    pub fn public_key(&self) -> PublicKey {
+        let pk = ed25519::to_public(&self.0);
+
+        PublicKey::from(pk)
+    }
+
+    /// create a `Signature` for the given message with this `SecretKey`.
+    ///
+    /// The `Signature` can then be verified against the associated `PublicKey`
+    /// and the original message.
+    pub fn sign<T: AsRef<[u8]>>(&self, msg: T) -> Signature {
+        let signature = ed25519::signature_extended(msg.as_ref(), &self.0);
+
+        Signature::from(signature)
+    }
+}
+
+impl PublicKey {
+    /// verify the cryptographic [`Signature`] against the `message` and the
+    /// [`PublicKey`] `self`.
+    ///
+    #[inline]
+    pub fn verify<T>(&self, message: T, signature: &Signature) -> bool
+    where
+        T: AsRef<[u8]>,
+    {
+        ed25519::verify(message.as_ref(), &self.0, signature.as_ref())
+    }
+}
+
+/* Drop ******************************************************************** */
+
+impl Drop for SecretKey {
+    fn drop(&mut self) {
+        self.0.scrub()
+    }
+}
+
+impl Drop for SecretKeyExtended {
+    fn drop(&mut self) {
+        self.0.scrub()
+    }
+}
+
+/* Format ****************************************************************** */
+
+impl fmt::Display for Signature {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&hex::encode(self.as_ref()))
+    }
+}
+
+impl fmt::Display for PublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&hex::encode(self.as_ref()))
+    }
+}
+
+impl fmt::Debug for Signature {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("Signature<Ed25519>")
+            .field(&hex::encode(self.as_ref()))
+            .finish()
+    }
+}
+
+impl fmt::Debug for PublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("PublicKey<Ed25519>")
+            .field(&hex::encode(self.as_ref()))
+            .finish()
+    }
+}
+
+macro_rules! impl_secret_fmt {
+    ($Type:ty) => {
+        /// conveniently provide a proper implementation to debug for the
+        /// SecretKey types when only *testing* the library
+        #[cfg(test)]
+        impl fmt::Debug for $Type {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.debug_tuple(&format!(
+                    "SecretKey<{typename}>",
+                    typename = type_name::<Self>()
+                ))
+                .field(&hex::encode(&self.0))
+                .finish()
+            }
+        }
+
+        /// conveniently provide an incomplete implementation of Debug for the
+        /// SecretKey.
+        #[cfg(not(test))]
+        impl fmt::Debug for $Type {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.debug_struct(&format!(
+                    "SecretKey<{typename}>",
+                    typename = type_name::<Self>()
+                ))
+                .finish_non_exhaustive()
+            }
+        }
+    };
+}
+
+impl_secret_fmt!(SecretKey);
+impl_secret_fmt!(SecretKeyExtended);
+
+/* AsRef ******************************************************************* */
+
+impl AsRef<[u8]> for PublicKey {
+    fn as_ref(&self) -> &[u8] {
+        self.0.as_ref()
+    }
+}
+
+impl AsRef<[u8]> for Signature {
+    fn as_ref(&self) -> &[u8] {
+        self.0.as_ref()
+    }
+}
+
+/* Conversion ************************************************************** */
+
+impl<'a> From<&'a Signature> for String {
+    fn from(s: &'a Signature) -> Self {
+        s.to_string()
+    }
+}
+
+impl From<Signature> for String {
+    fn from(s: Signature) -> Self {
+        s.to_string()
+    }
+}
+
+impl From<[u8; Self::SIZE]> for PublicKey {
+    fn from(bytes: [u8; Self::SIZE]) -> Self {
+        Self(bytes)
+    }
+}
+
+impl From<PublicKey> for [u8; PublicKey::SIZE] {
+    fn from(pk: PublicKey) -> Self {
+        pk.0
+    }
+}
+
+impl From<[u8; Self::SIZE]> for Signature {
+    fn from(bytes: [u8; Self::SIZE]) -> Self {
+        Self(bytes)
+    }
+}
+
+impl<'a> TryFrom<&'a [u8]> for PublicKey {
+    type Error = TryFromPublicKeyError;
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.len() != Self::SIZE {
+            Err(Self::Error::InvalidSize)
+        } else {
+            let mut s = Self::zero();
+            s.0.copy_from_slice(value);
+            Ok(s)
+        }
+    }
+}
+
+impl<'a> TryFrom<&'a [u8]> for Signature {
+    type Error = TryFromSignatureError;
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.len() != Self::SIZE {
+            Err(Self::Error::InvalidSize)
+        } else {
+            let mut s = Self::zero();
+            s.0.copy_from_slice(value);
+            Ok(s)
+        }
+    }
+}
+
+impl FromStr for PublicKey {
+    type Err = hex::FromHexError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut r = Self::zero();
+        hex::decode_to_slice(s, &mut r.0)?;
+        Ok(r)
+    }
+}
+
+impl FromStr for Signature {
+    type Err = hex::FromHexError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut r = Self::zero();
+        hex::decode_to_slice(s, &mut r.0)?;
+        Ok(r)
+    }
+}
+
+impl<'a> TryFrom<&'a str> for Signature {
+    type Error = <Self as FromStr>::Err;
+    fn try_from(s: &'a str) -> Result<Self, Self::Error> {
+        s.parse()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use quickcheck::{Arbitrary, Gen, TestResult};
+    use quickcheck_macros::quickcheck;
+
+    impl Arbitrary for SecretKey {
+        fn arbitrary(g: &mut Gen) -> Self {
+            let mut s = Self::zero();
+            s.0.iter_mut().for_each(|byte| {
+                *byte = u8::arbitrary(g);
+            });
+            s
+        }
+    }
+
+    impl Arbitrary for SecretKeyExtended {
+        fn arbitrary(g: &mut Gen) -> Self {
+            let mut s = Self::zero();
+            s.0.iter_mut().for_each(|byte| {
+                *byte = u8::arbitrary(g);
+            });
+
+            s.0[0] &= 0b1111_1000;
+            s.0[31] &= 0b0011_1111;
+            s.0[31] |= 0b0100_0000;
+
+            s
+        }
+    }
+
+    impl Arbitrary for PublicKey {
+        fn arbitrary(g: &mut Gen) -> Self {
+            let mut s = Self::zero();
+            s.0.iter_mut().for_each(|byte| {
+                *byte = u8::arbitrary(g);
+            });
+            s
+        }
+    }
+
+    impl Arbitrary for Signature {
+        fn arbitrary(g: &mut Gen) -> Self {
+            let mut s = Self::zero();
+            s.0.iter_mut().for_each(|byte| {
+                *byte = u8::arbitrary(g);
+            });
+            s
+        }
+    }
+
+    #[quickcheck]
+    fn signing_verify_works(signing_key: SecretKey, message: Vec<u8>) -> bool {
+        let public_key = signing_key.public_key();
+        let signature = signing_key.sign(&message);
+
+        public_key.verify(message, &signature)
+    }
+
+    #[quickcheck]
+    fn signing_verify_works_extended(signing_key: SecretKeyExtended, message: Vec<u8>) -> bool {
+        let public_key = signing_key.public_key();
+        let signature = signing_key.sign(&message);
+
+        public_key.verify(message, &signature)
+    }
+
+    #[quickcheck]
+    fn verify_random_signature_does_not_work(
+        public_key: PublicKey,
+        signature: Signature,
+        message: Vec<u8>,
+    ) -> bool {
+        // NOTE: this test may fail but it is impossible to see this happening in normal condition.
+        //       we are generating 32 random bytes of public key and 64 random bytes
+        //       of signature with an randomly generated message of a random number
+        //       of bytes in. If the message were empty, the probability to have
+        //       a signature that matches the verify key would still be 1 out of 2^96.
+        //
+        //       if this test fails and it is not a bug, go buy a lottery ticket.
+        !public_key.verify(message, &signature)
+    }
+
+    #[quickcheck]
+    fn public_key_try_from_correct_size(public_key: PublicKey) -> TestResult {
+        match PublicKey::try_from(public_key.as_ref()) {
+            Ok(_) => TestResult::passed(),
+            Err(TryFromPublicKeyError::InvalidSize) => {
+                TestResult::error("was expecting the test to pass")
+            }
+        }
+    }
+
+    #[quickcheck]
+    fn public_key_try_from_incorrect_size(bytes: Vec<u8>) -> TestResult {
+        if bytes.len() == PublicKey::SIZE {
+            return TestResult::discard();
+        }
+        match PublicKey::try_from(bytes.as_slice()) {
+            Ok(_) => TestResult::error(
+                "Expecting to fail with invalid size instead of having a valid value",
+            ),
+            Err(TryFromPublicKeyError::InvalidSize) => TestResult::passed(),
+        }
+    }
+
+    #[quickcheck]
+    fn signature_try_from_correct_size(signature: Signature) -> TestResult {
+        match Signature::try_from(signature.as_ref()) {
+            Ok(_) => TestResult::passed(),
+            Err(TryFromSignatureError::InvalidSize) => {
+                TestResult::error("was expecting the test to pass")
+            }
+        }
+    }
+
+    #[quickcheck]
+    fn signature_try_from_incorrect_size(bytes: Vec<u8>) -> TestResult {
+        if bytes.len() == Signature::SIZE {
+            return TestResult::discard();
+        }
+        match Signature::try_from(bytes.as_slice()) {
+            Ok(_) => TestResult::error(
+                "Expecting to fail with invalid size instead of having a valid value",
+            ),
+            Err(TryFromSignatureError::InvalidSize) => TestResult::passed(),
+        }
+    }
+
+    #[quickcheck]
+    fn public_key_from_str(public_key: PublicKey) -> TestResult {
+        let s = public_key.to_string();
+
+        match s.parse::<PublicKey>() {
+            Ok(decoded) => {
+                if decoded == public_key {
+                    TestResult::passed()
+                } else {
+                    TestResult::error("the decoded key is not equal")
+                }
+            }
+            Err(error) => TestResult::error(error.to_string()),
+        }
+    }
+
+    #[quickcheck]
+    fn signature_from_str(signature: Signature) -> TestResult {
+        let s = signature.to_string();
+
+        match s.parse::<Signature>() {
+            Ok(decoded) => {
+                if decoded == signature {
+                    TestResult::passed()
+                } else {
+                    TestResult::error("the decoded signature is not equal")
+                }
+            }
+            Err(error) => TestResult::error(error.to_string()),
+        }
+    }
+}

pallas-crypto/src/key/mod.rs

@@ -0,0 +1 @@
+pub mod ed25519;

pallas-crypto/src/lib.rs

@@ -1 +1,3 @@
 pub mod hash;
+pub mod key;
+pub mod memsec;

pallas-crypto/src/memsec.rs

@@ -0,0 +1,235 @@
+/*!
+# Memsec utility functions
+Most of the types defined here implements `Scrubbed` trait.
+*/
+
+use std::ptr;
+
+/// Types implementing this can be scrubbed, the memory is cleared and
+/// erased with a dummy value.
+pub trait Scrubbed {
+    fn scrub(&mut self);
+}
+
+/// Perform a secure memset. This function is guaranteed not to be elided
+/// or reordered.
+///
+/// # Performance consideration
+///
+/// On `nightly`, the function use a more efficient.
+///
+/// # Safety
+///
+/// The destination memory (`dst` to `dst+count`) must be properly allocated
+/// and ready to use.
+#[inline(never)]
+pub unsafe fn memset(dst: *mut u8, val: u8, count: usize) {
+    for i in 0..count {
+        ptr::write_volatile(dst.add(i), val);
+    }
+}
+
+/// compare the equality of the 2 given arrays, constant in time
+///
+/// # Panics
+///
+/// The function will panic if it is called with a `len` of 0.
+///
+/// # Safety
+///
+/// Expecting to have both valid pointer and the count to fit in
+/// both the allocated memories
+#[inline(never)]
+pub unsafe fn memeq(v1: *const u8, v2: *const u8, len: usize) -> bool {
+    let mut sum = 0;
+
+    assert!(
+        len != 0,
+        "Cannot perform equality comparison if the length is 0"
+    );
+
+    for i in 0..len {
+        let val1 = ptr::read_volatile(v1.add(i));
+        let val2 = ptr::read_volatile(v2.add(i));
+
+        let xor = val1 ^ val2;
+
+        sum |= xor;
+    }
+
+    sum == 0
+}
+
+/// Constant time comparison
+///
+/// # Panics
+///
+/// The function will panic if it is called with a `len` of 0.
+///
+/// # Safety
+///
+/// Expecting to have both valid pointer and the count to fit in
+/// both the allocated memories
+#[inline(never)]
+pub unsafe fn memcmp(v1: *const u8, v2: *const u8, len: usize) -> std::cmp::Ordering {
+    let mut res = 0;
+
+    assert!(
+        len != 0,
+        "Cannot perform ordering comparison if the length is 0"
+    );
+
+    for i in (0..len).rev() {
+        let val1 = ptr::read_volatile(v1.add(i)) as i32;
+        let val2 = ptr::read_volatile(v2.add(i)) as i32;
+        let diff = val1 - val2;
+        res = (res & (((diff - 1) & !diff) >> 8)) | diff;
+    }
+    let res = ((res - 1) >> 8) + (res >> 8) + 1;
+
+    res.cmp(&0)
+}
+
+macro_rules! impl_scrubbed_primitive {
+    ($t:ty) => {
+        impl Scrubbed for $t {
+            #[inline(never)]
+            fn scrub(&mut self) {
+                *self = 0;
+            }
+        }
+    };
+}
+
+impl_scrubbed_primitive!(u8);
+impl_scrubbed_primitive!(u16);
+impl_scrubbed_primitive!(u32);
+impl_scrubbed_primitive!(u64);
+impl_scrubbed_primitive!(u128);
+impl_scrubbed_primitive!(usize);
+impl_scrubbed_primitive!(i8);
+impl_scrubbed_primitive!(i16);
+impl_scrubbed_primitive!(i32);
+impl_scrubbed_primitive!(i64);
+impl_scrubbed_primitive!(i128);
+impl_scrubbed_primitive!(isize);
+
+macro_rules! impl_scrubbed_array {
+    ($t:ty) => {
+        impl Scrubbed for $t {
+            fn scrub(&mut self) {
+                unsafe { memset(self.as_mut_ptr(), 0, self.len()) }
+            }
+        }
+    };
+}
+
+impl_scrubbed_array!([u8]);
+impl_scrubbed_array!(str);
+
+impl<const N: usize> Scrubbed for [u8; N] {
+    fn scrub(&mut self) {
+        unsafe { memset(self.as_mut_ptr(), 0, self.len()) }
+    }
+}
+
+impl<T: Scrubbed> Scrubbed for Option<T> {
+    fn scrub(&mut self) {
+        self.as_mut().map(Scrubbed::scrub);
+    }
+}
+
+impl<T: Scrubbed> Scrubbed for Vec<T> {
+    fn scrub(&mut self) {
+        self.iter_mut().for_each(Scrubbed::scrub)
+    }
+}
+
+impl<T: Scrubbed> Scrubbed for Box<T> {
+    fn scrub(&mut self) {
+        self.as_mut().scrub()
+    }
+}
+
+impl<T: Scrubbed> Scrubbed for std::cell::Cell<T> {
+    fn scrub(&mut self) {
+        self.get_mut().scrub()
+    }
+}
+
+impl<T: Scrubbed> Scrubbed for std::cell::RefCell<T> {
+    fn scrub(&mut self) {
+        self.get_mut().scrub()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::cmp::Ordering;
+
+    use super::*;
+    use quickcheck::TestResult;
+    use quickcheck_macros::quickcheck;
+
+    #[test]
+    #[should_panic]
+    fn eq_empty() {
+        let bytes = Vec::new();
+        unsafe { memeq(bytes.as_ptr(), bytes.as_ptr(), bytes.len()) };
+    }
+
+    #[test]
+    #[should_panic]
+    fn ord_empty() {
+        let bytes = Vec::new();
+        unsafe { memcmp(bytes.as_ptr(), bytes.as_ptr(), bytes.len()) };
+    }
+
+    #[quickcheck]
+    fn eq(bytes: Vec<u8>) -> TestResult {
+        if bytes.is_empty() {
+            TestResult::discard()
+        } else {
+            let b = unsafe { memeq(bytes.as_ptr(), bytes.as_ptr(), bytes.len()) };
+            TestResult::from_bool(b)
+        }
+    }
+
+    #[quickcheck]
+    fn ord_eq(bytes: Vec<u8>) -> TestResult {
+        if bytes.is_empty() {
+            TestResult::discard()
+        } else {
+            let ord = unsafe { memcmp(bytes.as_ptr(), bytes.as_ptr(), bytes.len()) };
+            TestResult::from_bool(ord == Ordering::Equal)
+        }
+    }
+
+    #[quickcheck]
+    fn neq(a: Vec<u8>, b: Vec<u8>) -> TestResult {
+        let len = std::cmp::min(a.len(), b.len());
+
+        if a[..len] == b[..len] || len == 0 {
+            TestResult::discard()
+        } else {
+            let b = unsafe { memeq(a.as_ptr(), b.as_ptr(), len) };
+
+            TestResult::from_bool(!b)
+        }
+    }
+
+    #[quickcheck]
+    fn ord(a: Vec<u8>, b: Vec<u8>) -> TestResult {
+        let len = std::cmp::min(a.len(), b.len());
+
+        if len == 0 {
+            TestResult::discard()
+        } else {
+            let a = &a[..len];
+            let b = &b[..len];
+            let ord = unsafe { memcmp(a.as_ptr(), b.as_ptr(), len) };
+
+            TestResult::from_bool(ord == a.cmp(b))
+        }
+    }
+}