diff --git a/src/bin/ssh-keygen.rs b/src/bin/ssh-keygen.rs
index 714fee2..14349aa 100644
--- a/src/bin/ssh-keygen.rs
+++ b/src/bin/ssh-keygen.rs
@@ -3,7 +3,7 @@ use std::io::prelude::*;
 use std::fs::File;
 
 pub fn main() {
-    let keys = (ssh::key::RSA.generate_key_pair)(1024);
+    let keypair = (ssh::key::ED25519.generate_key_pair)(None);
     let mut buffer = File::create("key.pub").unwrap();
-    keys.0.write(&mut buffer);
+    keypair.export(&mut buffer);
 }
diff --git a/src/key/ed25519.rs b/src/key/ed25519.rs
new file mode 100644
index 0000000..8612e44
--- /dev/null
+++ b/src/key/ed25519.rs
@@ -0,0 +1,106 @@
+use key::{KeyPair, CryptoSystem};
+use std::io::{self, Read, Write};
+use rand::{self, Rng};
+use crypto::ed25519;
+
+pub static ED25519: CryptoSystem = CryptoSystem {
+    id: "ed25519",
+    generate_key_pair: Ed25519KeyPair::generate,
+    import: Ed25519KeyPair::import,
+    read_public: Ed25519KeyPair::read_public
+};
+
+struct Ed25519KeyPair {
+    private: Option<[u8;64]>,
+    public: [u8;32],
+}
+
+impl Ed25519KeyPair {
+    fn generate(_: Option<u32>) -> Box<KeyPair> {
+        let mut seed = [0u8;32];
+        let mut rng = rand::thread_rng();
+        rng.fill_bytes(&mut seed);
+
+        let (private, public) = ed25519::keypair(&seed);
+        Box::new(Ed25519KeyPair {
+            private: Some(private),
+            public: public
+        })
+    }
+
+    fn import(mut r: &mut Read) -> io::Result<Box<KeyPair>> {
+        use packet::ReadPacketExt;
+        let id = r.read_utf8()?;
+        assert_eq!(id, "ssh-ed25519");
+
+        let pub_len = r.read_uint32()?;
+        assert_eq!(pub_len, 32);
+
+        let mut public = [0u8;32];
+        r.read_exact(&mut public)?;
+
+        let priv_len = r.read_uint32()?;
+        assert_eq!(priv_len, 64);
+
+        let mut private = [0u8;64];
+        r.read_exact(&mut private)?;
+
+        Ok(Box::new(Ed25519KeyPair {
+            public: public,
+            private: Some(private)
+        }))
+    }
+
+    fn read_public(mut r: &mut Read) -> io::Result<Box<KeyPair>> {
+        use packet::ReadPacketExt;
+
+        let len = r.read_uint32()?;
+        assert_eq!(len, 32);
+
+        let mut public = [0u8;32];
+        r.read_exact(&mut public)?;
+
+        Ok(Box::new(Ed25519KeyPair {
+            private: None,
+            public: public
+        }))
+    }
+}
+
+impl KeyPair for Ed25519KeyPair {
+    fn system(&self) -> &'static CryptoSystem { &ED25519 }
+
+    fn has_private(&self) -> bool {
+        self.private.is_some()
+    }
+
+    fn verify(&self, data: &[u8], signature: &[u8]) -> Result<bool, ()> {
+        Ok(ed25519::verify(data, &self.public, signature))
+    }
+
+    fn sign(&self, data: &[u8]) -> Result<Vec<u8>, ()> {
+        if let Some(private_key) = self.private {
+            let signature = ed25519::signature(data, &private_key);
+            Ok(signature.to_vec())
+        }
+        else {
+            Err(())
+        }
+    }
+
+    fn write_public(&self, w: &mut Write) -> io::Result<()> {
+        use packet::WritePacketExt;
+        w.write_string("ssh-ed25519")?;
+        w.write_bytes(&self.public)
+    }
+
+    fn export(&self, w: &mut Write) -> io::Result<()> {
+        use packet::WritePacketExt;
+        w.write_string("ssh-ed25519")?;
+        w.write_bytes(&self.public)?;
+        if let Some(private_key) = self.private {
+            w.write_bytes(&private_key)?;
+        }
+        Ok(())
+    }
+}
diff --git a/src/key/mod.rs b/src/key/mod.rs
index 0c53a79..fd389a3 100644
--- a/src/key/mod.rs
+++ b/src/key/mod.rs
@@ -1,41 +1,26 @@
-use std::io::{Result, Read, Write};
+use std::io::{self, Read, Write};
 
-mod rsa;
+//mod rsa;
+mod ed25519;
 
-pub use self::rsa::RSA;
+//pub use self::rsa::RSA;
+pub use self::ed25519::ED25519;
 
-pub trait Key {
+pub trait KeyPair {
     fn system(&self) -> &'static CryptoSystem;
 
-    fn read(&self, r: &mut Read) -> Result<Box<Self>>
-    where
-        Self: Sized;
+    fn has_private(&self) -> bool;
 
-    fn import(&self, r: &mut Read) -> Result<Box<Self>>
-    where
-        Self: Sized,
-    {
-        self.read(r)
-    }
+    fn verify(&self, data: &[u8], signature: &[u8]) -> Result<bool, ()>;
+    fn sign(&self, data: &[u8]) -> Result<Vec<u8>, ()>;
 
-    fn write(&self, w: &mut Write) -> Result<()>;
-
-    fn export(&self, w: &mut Write) -> Result<()> {
-        self.write(w)
-    }
+    fn write_public(&self, w: &mut Write) -> io::Result<()>;
+    fn export(&self, w: &mut Write) -> io::Result<()>;
 }
 
-pub trait PublicKey: Key {
-    fn encrypt(&self, data: &[u8]) -> Vec<u8>;
-}
-
-pub trait PrivateKey: Key {
-    fn sign(&self, data: &[u8]) -> Vec<u8>;
-}
-
-type KeyPair = (Box<PublicKey>, Box<PrivateKey>);
-
 pub struct CryptoSystem {
     pub id: &'static str,
-    pub generate_key_pair: fn(bits: u32) -> KeyPair
+    pub generate_key_pair: fn(bits: Option<u32>) -> Box<KeyPair>,
+    pub import: fn(r: &mut Read) -> io::Result<Box<KeyPair>>,
+    pub read_public: fn(r: &mut Read) -> io::Result<Box<KeyPair>>
 }
diff --git a/src/key/rsa.rs b/src/key/rsa.rs
index 0598f16..4d92d40 100644
--- a/src/key/rsa.rs
+++ b/src/key/rsa.rs
@@ -2,7 +2,7 @@ use key::{Key, PublicKey, PrivateKey, KeyPair, CryptoSystem};
 use std::io::{Read, Write, Result};
 
 pub static RSA: CryptoSystem = CryptoSystem {
-    id: "ssh-rsa",
+    id: "rsa",
     generate_key_pair: generate_key_pair,
 };
 
diff --git a/src/lib.rs b/src/lib.rs
index 1cec66e..6ccc8ae 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,5 @@
 extern crate byteorder;
 extern crate rand;
-extern crate ring;
 extern crate crypto;
 extern crate num_bigint;
 #[macro_use]
diff --git a/src/packet.rs b/src/packet.rs
index b026711..d33335d 100644
--- a/src/packet.rs
+++ b/src/packet.rs
@@ -126,11 +126,15 @@ pub trait WritePacketExt: WriteBytesExt {
 
     fn write_string(&mut self, s: &str) -> Result<()> {
         let bytes = s.as_bytes();
+        self.write_bytes(bytes)
+    }
+
+    fn write_bytes(&mut self, bytes: &[u8]) -> Result<()> {
         self.write_u32::<BigEndian>(bytes.len() as u32)?;
         self.write_all(bytes)
     }
 
-    fn write_bytes(&mut self, bytes: &[u8]) -> Result<()> {
+    fn write_raw_bytes(&mut self, bytes: &[u8]) -> Result<()> {
         self.write_all(bytes)
     }
 
@@ -140,7 +144,6 @@ pub trait WritePacketExt: WriteBytesExt {
 
     fn write_mpint(&mut self, value: BigInt) -> Result<()> {
         let bytes = value.to_signed_bytes_be();
-        self.write_u32::<BigEndian>(bytes.len() as u32)?;
         self.write_bytes(bytes.as_slice())
     }
 
diff --git a/src/session.rs b/src/session.rs
index be12b3b..bf9bac8 100644
--- a/src/session.rs
+++ b/src/session.rs
@@ -91,7 +91,7 @@ impl<W: Write> Session<W> {
 
         let mut packet = Packet::new(MessageType::KexInit);
         packet.with_writer(&|w| {
-            w.write_bytes(cookie.as_slice());
+            w.write_raw_bytes(cookie.as_slice());
             w.write_list(KEY_EXCHANGE);
             w.write_list(HOST_KEY);
             w.write_list(ENCRYPTION);
diff --git a/tests/crypto_systems.rs b/tests/crypto_systems.rs
new file mode 100644
index 0000000..8462742
--- /dev/null
+++ b/tests/crypto_systems.rs
@@ -0,0 +1,29 @@
+extern crate ssh;
+extern crate rand;
+
+use rand::Rng;
+use std::io::Cursor;
+use ssh::key::{self, CryptoSystem, KeyPair};
+
+fn test_export_import(keypair: &Box<KeyPair>) -> Box<KeyPair> {
+    let mut buffer = Vec::new();
+    keypair.export(&mut buffer).unwrap();
+
+    (keypair.system().import)(&mut Cursor::new(buffer)).unwrap()
+}
+
+fn test_crypto_system(system: &CryptoSystem, key_size: Option<u32>) {
+    let keypair = (system.generate_key_pair)(key_size);
+    let keypair2 = test_export_import(&keypair);
+
+    let mut buffer = [0;4096];
+    let mut rng = rand::thread_rng();
+    rng.fill_bytes(&mut buffer);
+
+    let signature = keypair.sign(&buffer).unwrap();
+    let verified = keypair2.verify(&buffer, signature.as_slice()).unwrap();
+    assert!(verified)
+}
+
+#[test]
+fn test_ed25519() { test_crypto_system(&key::ED25519, None); }