diff --git a/Cargo.toml b/Cargo.toml
index 8eb15389d..ab0c8fbf5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ members = [
     "sha1",
     "sha2",
     "sha3",
+    "skein",
     "streebog",
     "whirlpool",
 ]
diff --git a/skein/Cargo.toml b/skein/Cargo.toml
new file mode 100644
index 000000000..e54e67481
--- /dev/null
+++ b/skein/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "skein"
+version = "0.3.0"
+authors = ["Kaz Wesley <keziahw@gmail.com>"]
+license = "MIT/Apache-2.0"
+description = "Skein hash functions"
+repository = "https://github.com/RustCrypto/hashes"
+keywords = ["crypto", "skein", "hash", "digest"]
+categories = ["cryptography", "no-std"]
+
+[dependencies]
+block-buffer = "0.7"
+block-padding = "0.1.0"
+digest = "0.8"
+threefish = { git = "git://github.com/kazcw/RustCrypto-block-ciphers", branch = "threefish", version = "0.3.0" }
+
+[dev-dependencies]
+digest = { version = "0.8", features = ["dev"] }
diff --git a/skein/src/lib.rs b/skein/src/lib.rs
new file mode 100644
index 000000000..04410b8a5
--- /dev/null
+++ b/skein/src/lib.rs
@@ -0,0 +1,224 @@
+// copyright 2017 Kaz Wesley
+
+#![no_std]
+
+extern crate block_buffer;
+extern crate block_padding;
+extern crate threefish;
+pub extern crate digest;
+
+pub use digest::generic_array::GenericArray;
+pub use digest::Digest;
+
+use block_buffer::BlockBuffer;
+use block_buffer::byteorder::{ByteOrder, LE};
+use block_padding::ZeroPadding;
+use digest::generic_array::typenum::{NonZero, PartialDiv, Unsigned, U128, U32, U64, U8};
+use digest::generic_array::ArrayLength;
+use threefish::{BlockCipher, Threefish1024, Threefish256, Threefish512};
+
+/// N word buffer.
+#[derive(Copy, Clone)]
+union Block<N>
+where
+    N: ArrayLength<u8>,
+    N: PartialDiv<U8>,
+    <N as PartialDiv<U8>>::Output: ArrayLength<u64>,
+    N::ArrayType: Copy,
+    <<N as PartialDiv<U8>>::Output as ArrayLength<u64>>::ArrayType: Copy,
+{
+    bytes: GenericArray<u8, N>,
+    words: GenericArray<u64, <N as PartialDiv<U8>>::Output>,
+}
+
+impl<N> Block<N>
+where
+    N: ArrayLength<u8>,
+    N: PartialDiv<U8>,
+    <N as PartialDiv<U8>>::Output: ArrayLength<u64>,
+    N::ArrayType: Copy,
+    <<N as PartialDiv<U8>>::Output as ArrayLength<u64>>::ArrayType: Copy,
+{
+    fn bytes(&mut self) -> &[u8] {
+        self.as_byte_array().as_slice()
+    }
+
+    fn as_byte_array(&self) -> &GenericArray<u8, N> {
+        unsafe { &self.bytes }
+    }
+
+    fn as_byte_array_mut(&mut self) -> &mut GenericArray<u8, N> {
+        unsafe { &mut self.bytes }
+    }
+
+    fn from_byte_array(block: &GenericArray<u8, N>) -> Self {
+        Block { bytes: *block }
+    }
+}
+
+impl<N> Default for Block<N>
+where
+    N: ArrayLength<u8>,
+    N: PartialDiv<U8>,
+    <N as PartialDiv<U8>>::Output: ArrayLength<u64>,
+    N::ArrayType: Copy,
+    <<N as PartialDiv<U8>>::Output as ArrayLength<u64>>::ArrayType: Copy,
+{
+    fn default() -> Self {
+        Block { words: GenericArray::default() }
+    }
+}
+
+impl<N> core::ops::BitXor<Block<N>> for Block<N>
+where
+    N: ArrayLength<u8>,
+    N: PartialDiv<U8>,
+    <N as PartialDiv<U8>>::Output: ArrayLength<u64>,
+    N::ArrayType: Copy,
+    <<N as PartialDiv<U8>>::Output as ArrayLength<u64>>::ArrayType: Copy,
+{
+    type Output = Block<N>;
+    fn bitxor(mut self, rhs: Block<N>) -> Self::Output {
+        // XOR is endian-agnostic
+        for (s, r) in unsafe { &mut self.words }.iter_mut().zip(unsafe { &rhs.words }) {
+            *s ^= *r;
+        }
+        self
+    }
+}
+
+#[derive(Clone)]
+struct State<X> {
+    t: (u64, u64),
+    x: X,
+}
+
+impl<X> State<X> {
+    fn new(t1: u64, x: X) -> Self {
+        let t = (0, t1);
+        State { t, x }
+    }
+}
+
+impl<X> core::fmt::Debug for State<X> {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+        f.debug_struct("State<X>")
+            .field("t", &"(unknown)")
+            .field("x", &"(unknown)")
+            .finish()
+    }
+}
+
+const VERSION: u64 = 1;
+const ID_STRING_LE: u64 = 0x33414853;
+const SCHEMA_VER: u64 = (VERSION << 32) | ID_STRING_LE;
+const CFG_TREE_INFO_SEQUENTIAL: u64 = 0;
+const T1_FLAG_FIRST: u64 = 1 << 62;
+const T1_FLAG_FINAL: u64 = 1 << 63;
+const T1_BLK_TYPE_CFG: u64 = 4 << 56;
+const T1_BLK_TYPE_MSG: u64 = 48 << 56;
+const T1_BLK_TYPE_OUT: u64 = 63 << 56;
+const CFG_STR_LEN: usize = 4 * 8;
+
+macro_rules! define_hasher {
+    ($name:ident, $threefish:ident, $state_bytes:ty, $state_bits:expr) => {
+        #[derive(Clone)]
+        pub struct $name<N: Unsigned+ArrayLength<u8>+NonZero+Default> {
+            state: State<Block<$state_bytes>>,
+            buffer: BlockBuffer<$state_bytes>,
+            _output: core::marker::PhantomData<GenericArray<u8, N>>
+        }
+
+        impl<N> core::fmt::Debug for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default {
+            fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+                f.debug_struct("Skein")
+                    .field("state", &self.state)
+                    .field("buffer.position()", &self.buffer.position())
+                    .finish()
+            }
+        }
+
+        impl<N> $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default {
+            fn process_block(state: &mut State<Block<$state_bytes>>,
+                             block: &GenericArray<u8, $state_bytes>, byte_count_add: usize) {
+                let block = Block::from_byte_array(block);
+                state.t.0 += byte_count_add as u64;
+                let fish = $threefish::with_tweak(state.x.as_byte_array(), state.t.0, state.t.1);
+                let mut x = block.clone();
+                fish.encrypt_block(x.as_byte_array_mut());
+                state.x = x ^ block;
+                state.t.1 &= !T1_FLAG_FIRST;
+            }
+        }
+
+        impl<N> Default for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default {
+            fn default() -> Self {
+                // build and process config block
+                let mut state = State::new(T1_FLAG_FIRST | T1_BLK_TYPE_CFG | T1_FLAG_FINAL, Block::default());
+                let mut cfg = GenericArray::<u8, $state_bytes>::default();
+                LE::write_u64(&mut cfg[..8], SCHEMA_VER);
+                LE::write_u64(&mut cfg[8..16], N::to_u64() * 8);
+                LE::write_u64(&mut cfg[16..24], CFG_TREE_INFO_SEQUENTIAL);
+                Self::process_block(&mut state, &cfg, CFG_STR_LEN);
+
+                // The chaining vars ctx->X are now initialized for the given hashBitLen.
+                // Set up to process the data message portion of the hash (default)
+                state.t = Default::default();
+                state.t.1 = T1_FLAG_FIRST | T1_BLK_TYPE_MSG;
+                Self {
+                    state,
+                    buffer: Default::default(),
+                    _output: Default::default()
+                }
+            }
+        }
+
+        impl<N> digest::BlockInput for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default  {
+            type BlockSize = <$threefish as BlockCipher>::BlockSize;
+        }
+
+        impl<N> digest::Input for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default  {
+            fn input<T: AsRef<[u8]>>(&mut self, data: T) {
+                let buffer = &mut self.buffer;
+                let state = &mut self.state;
+                buffer.input_lazy(data.as_ref(), |block| Self::process_block(state, block, $state_bits/8));
+            }
+        }
+
+        impl<N> digest::FixedOutput for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default  {
+            type OutputSize = N;
+
+            fn fixed_result(mut self) -> GenericArray<u8, N> {
+                self.state.t.1 |= T1_FLAG_FINAL;
+                let pos = self.buffer.position();
+                let final_block = self.buffer.pad_with::<ZeroPadding>().unwrap();
+                Self::process_block(&mut self.state, final_block, pos);
+
+                // run Threefish in "counter mode" to generate output
+                let mut output = GenericArray::default();
+                for (i, chunk) in output.chunks_mut($state_bits / 8).enumerate() {
+                    let mut ctr = State::new(T1_FLAG_FIRST | T1_BLK_TYPE_OUT | T1_FLAG_FINAL, self.state.x);
+                    let mut b = GenericArray::<u8, $state_bytes>::default();
+                    LE::write_u64(&mut b[..8], i as u64);
+                    Self::process_block(&mut ctr, &b, 8);
+                    let n = chunk.len();
+                    chunk.copy_from_slice(&ctr.x.bytes()[..n]);
+                }
+                output
+            }
+        }
+
+        impl<N> digest::Reset for $name<N> where N: Unsigned+ArrayLength<u8>+NonZero+Default {
+            fn reset(&mut self) {
+                *self = Self::default();
+            }
+        }
+    }
+}
+
+#[cfg_attr(rustfmt, skip)]
+define_hasher!(Skein256, Threefish256, U32, 256);
+#[cfg_attr(rustfmt, skip)]
+define_hasher!(Skein512, Threefish512, U64, 512);
+#[cfg_attr(rustfmt, skip)]
+define_hasher!(Skein1024, Threefish1024, U128, 1024);
diff --git a/skein/tests/data/skein1024_32.blb b/skein/tests/data/skein1024_32.blb
new file mode 100644
index 000000000..3b750ac6a
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diff --git a/skein/tests/data/skein1024_64.blb b/skein/tests/data/skein1024_64.blb
new file mode 100644
index 000000000..20b79238f
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diff --git a/skein/tests/data/skein256_32.blb b/skein/tests/data/skein256_32.blb
new file mode 100644
index 000000000..13a6f6b38
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diff --git a/skein/tests/data/skein256_64.blb b/skein/tests/data/skein256_64.blb
new file mode 100644
index 000000000..7f05f1268
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diff --git a/skein/tests/data/skein512_32.blb b/skein/tests/data/skein512_32.blb
new file mode 100644
index 000000000..972253349
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diff --git a/skein/tests/data/skein512_64.blb b/skein/tests/data/skein512_64.blb
new file mode 100644
index 000000000..58e7057ee
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diff --git a/skein/tests/lib.rs b/skein/tests/lib.rs
new file mode 100644
index 000000000..c9c249ba3
--- /dev/null
+++ b/skein/tests/lib.rs
@@ -0,0 +1,14 @@
+#![no_std]
+extern crate skein;
+#[macro_use]
+extern crate digest;
+
+use digest::dev::digest_test;
+use digest::generic_array::typenum::{U32, U64};
+
+new_test!(skein256_32, "skein256_32", skein::Skein256<U32>, digest_test);
+new_test!(skein512_32, "skein512_32", skein::Skein512<U32>, digest_test);
+new_test!(skein1024_32, "skein1024_32", skein::Skein1024<U32>, digest_test);
+new_test!(skein256_64, "skein256_64", skein::Skein256<U64>, digest_test);
+new_test!(skein512_64, "skein512_64", skein::Skein512<U64>, digest_test);
+new_test!(skein1024_64, "skein1024_64", skein::Skein1024<U64>, digest_test);