Add trait for KEMs and DH functions

README.md

@@ -34,4 +34,8 @@ The following primitives are covered:
    - Cryptographically secure, deterministic RNG
 
  - Asymmetric Signer
-   - Normal signer
+   - Normal signer
+
+ - Diffie-Hellman
+
+ - Key Encapsulation Mechanism

src/dh.rs

@@ -0,0 +1,25 @@
+use crate::rng::{SecKeyGen, PubKeyGen};
+use std::error::Error;
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+/// Information about a Diffie-Hellman group
+pub struct DiffieHellmanInfo {
+	/// The name
+	pub name: &'static str,
+
+	/// The secret key length
+	pub sec_key_len: usize,
+	/// The public key length
+	pub pub_key_len: usize,
+	/// The shared secret length
+	pub ss_len: usize,
+}
+
+/// A Diffie-Hellman interface
+pub trait DiffieHellman: SecKeyGen + PubKeyGen {
+	fn info(&self) -> DiffieHellmanInfo;
+
+	/// Combine `pub_key` with a `sec_key` and store the shared secret to `buf`
+	fn dh(&self, buf: &mut [u8], pub_key: &[u8], sec_key: &[u8])
+		-> Result<(), Box<dyn Error + 'static>>;
+}

src/kem.rs

@@ -0,0 +1,29 @@
+use crate::rng::{SecKeyGen, PubKeyGen};
+
+/// Information about a Key Encapsulation Mechanism implementation
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct KEMInfo {
+	pub name: 'static str,
+
+	/// Length of public key
+	pub pub_key_len: usize,
+	/// Length of private key
+	pub sec_key_len: usize,
+	/// Length of the encapsulated secret
+	pub ctext_len: usize,
+	/// Length of the shared secred
+	pub ss_len: usize,
+}
+
+pub trait KEM: SecKeyGen + PubKeyGen {
+	/// Returns information about the Key Encapsulation Mechanism
+	fn info(&self) -> KEMInfo;
+
+	/// Encapsulates to `pub_key`, stores ciphertext to `ctext` and shared secret to `ss`
+	fn encapsulate(&self, ctext: &mut[u8], ss: &mut[u8], pub_key: &[u8], rng: &mut SecureRng)
+		-> Result<(), Box<dyn Error + 'static>>;
+
+	/// Decrypts the encapsulated `ctext` into `ss` using `sec_key`
+	fn decapsulate(&self, ss: &mut[u8], ctext: &[u8], sec_key: &[u8])
+		-> Result<(), Box<dyn Error + 'static>>;
+}

src/rng.rs

@@ -23,12 +23,12 @@ pub trait DeterministicRng: SecureRng {
 /// A algorithm specific key generator to generate a (secret) key
 pub trait SecKeyGen {
 	/// Generates a new key into `buf` using `rng` and returns the length of the secret key
-	fn new_sec_key(&self, buf: &mut[u8], rng: &mut SecureRng)
+	fn new_sec_key(&self, buf: &mut[u8], rng: &mut dyn SecureRng)
 		-> Result<usize, Box<dyn Error + 'static>>;
 }
 
 /// A algorithm specific trait to compute a public key from a secret key
 pub trait PubKeyGen {
 	/// Computes the public key from `sec_key` into `buf` and returns the length of the public key
 	fn get_pub_key(&self, buf: &mut[u8], sec_key: &[u8]) -> Result<usize, Box<dyn Error + 'static>>;
-}
+}