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authorАртём Павлов [Artyom Pavlov] <newpavlov@gmail.com>2017-08-14 07:37:17 +0300
committerАртём Павлов [Artyom Pavlov] <newpavlov@gmail.com>2017-08-14 07:37:17 +0300
commit331727194c231a10dc2e296922e09aa0e888f4bd (patch)
tree46e2a32679f399a7584b3b33d3986611195a395c /srp/src
parentdefd41c0ee00cf06930b733e9ab06163bc6ad1cf (diff)
downloadPAKEs-331727194c231a10dc2e296922e09aa0e888f4bd.tar.xz
PAKE repository reorganization
Diffstat (limited to 'srp/src')
-rw-r--r--srp/src/client.rs212
-rw-r--r--srp/src/groups.rs56
-rw-r--r--srp/src/groups/1024.bin3
-rw-r--r--srp/src/groups/1536.bin1
-rw-r--r--srp/src/groups/2048.bin2
-rw-r--r--srp/src/groups/3072.binbin0 -> 384 bytes
-rw-r--r--srp/src/groups/4096.binbin0 -> 512 bytes
-rw-r--r--srp/src/groups/6144.binbin0 -> 768 bytes
-rw-r--r--srp/src/groups/8192.binbin0 -> 1024 bytes
-rw-r--r--srp/src/k_sha1_1024.bin1
-rw-r--r--srp/src/lib.rs79
-rw-r--r--srp/src/prime.bin1
-rw-r--r--srp/src/server.rs136
-rw-r--r--srp/src/tools.rs19
-rw-r--r--srp/src/types.rs64
15 files changed, 574 insertions, 0 deletions
diff --git a/srp/src/client.rs b/srp/src/client.rs
new file mode 100644
index 0000000..4348f4f
--- /dev/null
+++ b/srp/src/client.rs
@@ -0,0 +1,212 @@
+//! SRP client implementation.
+//!
+//! # Usage
+//! First create SRP client struct by passing to it SRP parameters (shared
+//! between client and server) and randomly generated `a`:
+//!
+//! ```ignore
+//! use srp::groups::G_2048;
+//! use sha2::Sha256;
+//!
+//! let a = rng.gen_iter::<u8>().take(64).collect::<Vec<u8>>();
+//! let client = SrpClient::<Sha256>::new(&a, &G_2048);
+//! ```
+//!
+//! Next send handshake data (username and `a_pub`) to the server and receive
+//! `salt` and `b_pub`:
+//!
+//! ```ignore
+//! let a_pub = client.get_a_pub();
+//! let (salt, b_pub) = conn.send_handshake(username, a_pub);
+//! ```
+//!
+//! Compute private key using `salt` with any password hashing function.
+//! You can use method from SRP-6a, but it's recommended to use specialized
+//! password hashing algorithm instead (e.g. PBKDF2, argon2 or scrypt).
+//! Next create verifier instance, note that `get_verifier` consumes client and
+//! can return error in case of malicious `b_pub`.
+//!
+//! ```ignore
+//! let private_key = srp_private_key::<Sha256>(username, password, salt);
+//! let verifier = client.get_verifier(&private_key, &b_pub)?;
+//! ```
+//!
+//! Finally verify the server: first generate user proof,
+//! send it to the server and verify server proof in the reply. Note that
+//! `verify_server` method will return error in case of incorrect server reply.
+//!
+//! ```ignore
+//! let user_proof = verifier.get_proof();
+//! let server_proof = conn.send_proof(user_proof);
+//! let key = verifier.verify_server(server_proof)?;
+//! ```
+//!
+//! `key` contains shared secret key between user and the server. Alternatively
+//! you can directly extract shared secret key using `get_key()` method and
+//! handle authentification through different (secure!) means (e.g. by using
+//! authentificated cipher mode).
+//!
+//! For user registration on the server first generate salt (e.g. 32 bytes long)
+//! and get password verifier which depends on private key. Send useranme, salt
+//! and password verifier over protected channel to protect against MitM for
+//! registration.
+//!
+//! ```ignore
+//! let pwd_verifier = client.get_password_verifier(&private_key);
+//! conn.send_registration_data(username, salt, pwd_verifier);
+//! ```
+
+//let buf = rng.gen_iter::<u8>().take(l).collect::<Vec<u8>>();
+use std::marker::PhantomData;
+
+use num::{BigUint, Zero};
+use digest::Digest;
+use generic_array::GenericArray;
+
+use tools::powm;
+use types::{SrpAuthError, SrpGroup};
+
+/// SRP client state before handshake with the server.
+pub struct SrpClient<'a, D: Digest> {
+ params: &'a SrpGroup,
+
+ a: BigUint,
+ a_pub: BigUint,
+
+ d: PhantomData<D>
+}
+
+/// SRP client state after handshake with the server.
+pub struct SrpClientVerifier<D: Digest> {
+ proof: GenericArray<u8, D::OutputSize>,
+ server_proof: GenericArray<u8, D::OutputSize>,
+ key: GenericArray<u8, D::OutputSize>,
+}
+
+/// Compute user private key as described in the RFC 5054. Consider using proper
+/// password hashing algorithm instead.
+pub fn srp_private_key<D: Digest>(username: &[u8], password: &[u8], salt: &[u8])
+ -> GenericArray<u8, D::OutputSize>
+{
+ let p = {
+ let mut d = D::new();
+ d.input(username);
+ d.input(b":");
+ d.input(password);
+ d.result()
+ };
+ let mut d = D::new();
+ d.input(salt);
+ d.input(&p);
+ d.result()
+}
+
+impl<'a, D: Digest> SrpClient<'a, D> {
+ /// Create new SRP client instance.
+ pub fn new(a: &[u8], params: &'a SrpGroup) -> Self {
+ let a = BigUint::from_bytes_be(a);
+ let a_pub = params.powm(&a);
+
+ Self { params, a, a_pub, d: Default::default() }
+ }
+
+ /// Get password verfier for user registration on the server
+ pub fn get_password_verifier(&self, private_key: &[u8]) -> Vec<u8> {
+ let x = BigUint::from_bytes_be(&private_key);
+ let v = self.params.powm(&x);
+ v.to_bytes_be()
+ }
+
+ fn calc_key(&self, b_pub: &BigUint, x: &BigUint, u: &BigUint)
+ -> GenericArray<u8, D::OutputSize>
+ {
+ let n = &self.params.n;
+ let k = self.params.compute_k::<D>();
+ let interm = (k * self.params.powm(x)) % n;
+ // Because we do operation in modulo N we can get: (kv + g^b) < kv
+ let v = if b_pub > &interm {
+ (b_pub - &interm) % n
+ } else {
+ (n + b_pub - &interm) % n
+ };
+ // S = |B - kg^x| ^ (a + ux)
+ let s = powm(&v, &(&self.a + (u*x) % n ), n);
+ D::digest(&s.to_bytes_be())
+ }
+
+ /// Process server reply to the handshake.
+ pub fn process_reply(self, private_key: &[u8], b_pub: &[u8])
+ -> Result<SrpClientVerifier<D>, SrpAuthError>
+ {
+ let u = {
+ let mut d = D::new();
+ d.input(&self.a_pub.to_bytes_be());
+ d.input(b_pub);
+ BigUint::from_bytes_be(&d.result())
+ };
+
+ let b_pub = BigUint::from_bytes_be(b_pub);
+
+ // Safeguard against malicious B
+ if &b_pub % &self.params.n == BigUint::zero() {
+ return Err(SrpAuthError{ description: "Malicious b_pub value" })
+ }
+
+ let x = BigUint::from_bytes_be(&private_key);
+ let key = self.calc_key(&b_pub, &x, &u);
+ // M1 = H(A, B, K)
+ let proof = {
+ let mut d = D::new();
+ d.input(&self.a_pub.to_bytes_be());
+ d.input(&b_pub.to_bytes_be());
+ d.input(&key);
+ d.result()
+ };
+
+ // M2 = H(A, M1, K)
+ let server_proof = {
+ let mut d = D::new();
+ d.input(&self.a_pub.to_bytes_be());
+ d.input(&proof);
+ d.input(&key);
+ d.result()
+ };
+
+ Ok(SrpClientVerifier {
+ proof: proof,
+ server_proof: server_proof,
+ key: key,
+ })
+ }
+
+ /// Get public ephemeral value for handshaking with the server.
+ pub fn get_a_pub(&self) -> Vec<u8> {
+ self.a_pub.to_bytes_be()
+ }
+}
+
+impl<D: Digest> SrpClientVerifier<D> {
+ /// Get shared secret key without authenticating server, e.g. for using with
+ /// authenticated encryption modes. DO NOT USE this method without
+ /// some kind of secure authentification.
+ pub fn get_key(self) -> GenericArray<u8, D::OutputSize> {
+ self.key
+ }
+
+ /// Verification data for sending to the server.
+ pub fn get_proof(&self) -> GenericArray<u8, D::OutputSize> {
+ self.proof.clone()
+ }
+
+ /// Verify server reply to verification data. It will return shared secret
+ /// key in case of success.
+ pub fn verify_server(self, reply: &[u8])
+ -> Result<GenericArray<u8, D::OutputSize>, SrpAuthError>
+ {
+ if self.server_proof.as_slice() != reply {
+ Err(SrpAuthError{ description: "Incorrect server proof" })
+ } else {
+ Ok(self.key)
+ }
+ }
+}
diff --git a/srp/src/groups.rs b/srp/src/groups.rs
new file mode 100644
index 0000000..246134e
--- /dev/null
+++ b/srp/src/groups.rs
@@ -0,0 +1,56 @@
+//! Groups from [RFC 5054](https://tools.ietf.org/html/rfc5054)
+//!
+//! It is strongly recommended to use them instead of custom generated
+//! groups. Additionally it is not recommended to use `G_1024` and `G_1536`,
+//! they are provided only for compatability with the legacy software.
+use types::SrpGroup;
+use num::BigUint;
+
+lazy_static! {
+ pub static ref G_1024: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/1024.bin")),
+ g: BigUint::from_bytes_be(&[2]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_1536: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/1536.bin")),
+ g: BigUint::from_bytes_be(&[2]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_2048: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/2048.bin")),
+ g: BigUint::from_bytes_be(&[2]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_3072: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/3072.bin")),
+ g: BigUint::from_bytes_be(&[5]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_4096: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/4096.bin")),
+ g: BigUint::from_bytes_be(&[5]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_6144: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/6144.bin")),
+ g: BigUint::from_bytes_be(&[5]),
+ };
+}
+
+lazy_static! {
+ pub static ref G_8192: SrpGroup = SrpGroup {
+ n: BigUint::from_bytes_be(include_bytes!("groups/8192.bin")),
+ g: BigUint::from_bytes_be(&[19]),
+ };
+}
diff --git a/srp/src/groups/1024.bin b/srp/src/groups/1024.bin
new file mode 100644
index 0000000..7ce0aa3
--- /dev/null
+++ b/srp/src/groups/1024.bin
@@ -0,0 +1,3 @@
+
+֜3
+`rau< 1L%evtt8;H֒PI\`]״aTֶΎi]IU){)ffWh<rl/nQ8vC[/ \ No newline at end of file
diff --git a/srp/src/groups/1536.bin b/srp/src/groups/1536.bin
new file mode 100644
index 0000000..c3a5972
--- /dev/null
+++ b/srp/src/groups/1536.bin
@@ -0,0 +1 @@
+<9'z*{ۥLaKM_O_Un'QƩK`z)X;CU"|gЁ4ȹy` 㺶=GTűvN?KSݝ>+n94'/=$Ćew.C}lBsJ̷|&J㩾/鸵).Z^G碌$BI#Mv5 \ No newline at end of file
diff --git a/srp/src/groups/2048.bin b/srp/src/groups/2048.bin
new file mode 100644
index 0000000..23207c6
--- /dev/null
+++ b/srp/src/groups/2048.bin
@@ -0,0 +1,2 @@
+kA2Jf^X/re1=`Ps)˴큓uwg=#K1 HP9ig`:f)/ Uy^ t
+tsYA>(Dkw;ʗ:#v zCldҹF[2wHTE#$}^z'u,/xa`'z毇NsS){*VÂq5؟z5#mR_Tuer֎Js \ No newline at end of file
diff --git a/srp/src/groups/3072.bin b/srp/src/groups/3072.bin
new file mode 100644
index 0000000..7e1a84d
--- /dev/null
+++ b/srp/src/groups/3072.bin
Binary files differ
diff --git a/srp/src/groups/4096.bin b/srp/src/groups/4096.bin
new file mode 100644
index 0000000..82463c0
--- /dev/null
+++ b/srp/src/groups/4096.bin
Binary files differ
diff --git a/srp/src/groups/6144.bin b/srp/src/groups/6144.bin
new file mode 100644
index 0000000..83a559a
--- /dev/null
+++ b/srp/src/groups/6144.bin
Binary files differ
diff --git a/srp/src/groups/8192.bin b/srp/src/groups/8192.bin
new file mode 100644
index 0000000..b1f32ac
--- /dev/null
+++ b/srp/src/groups/8192.bin
Binary files differ
diff --git a/srp/src/k_sha1_1024.bin b/srp/src/k_sha1_1024.bin
new file mode 100644
index 0000000..4408438
--- /dev/null
+++ b/srp/src/k_sha1_1024.bin
@@ -0,0 +1 @@
+uVZ,f\>o \ No newline at end of file
diff --git a/srp/src/lib.rs b/srp/src/lib.rs
new file mode 100644
index 0000000..df11ae9
--- /dev/null
+++ b/srp/src/lib.rs
@@ -0,0 +1,79 @@
+//! [Secure Remote Password][1] (SRP) protocol implementation.
+//!
+//! This implementation is generic over hash functions using
+//! [`Digest`](https://docs.rs/digest) trait, so you will need to choose a hash
+//! function, e.g. `Sha256` from [`sha2`](https://crates.io/crates/sha2) crate.
+//! Additionally this crate allows to use a specialized password hashing
+//! algorithm for private key computation instead of method described in the
+//! SRP literature.
+//!
+//! Compatability with over implementations was not yet tested.
+//!
+//! # Usage
+//! Add `srp` dependecy to your `Cargo.toml`:
+//!
+//! ```toml
+//! [dependencies]
+//! rand = "0.3"
+//! ```
+//!
+//! and this to your crate root:
+//!
+//! ```rust
+//! extern crate srp;
+//! ```
+//!
+//! Next read documentation for [`client`](client/index.html) and
+//! [`server`](server/index.html) modules.
+//!
+//! # Algorithm description
+//! Here we briefly describe implemented algroithm. For additionall information
+//! refer to SRP literature. All arithmetic is done modulo `N`, where `N` is a
+//! large safe prime (`N = 2q+1`, where `q` is prime). Additionally `g` MUST be
+//! a generator modulo `N`. It's STRONGLY recommended to use SRP parameters
+//! provided by this crate in the [`groups`](groups/index.html) module.
+//!
+//! Client | | Server
+//! ------------------------|---------------|------------------------
+//! | — `I` —> | (lookup `s`, `v`)
+//! `x = PH(P, s)` | <— `s`, `v` — |
+//! `a_pub = g^a` | — `a_pub` —> | `b_pub = k*v + g^b`
+//! `u = H(a_pub || b_pub)` | <— `b_pub` — | `u = H(a_pub || b_pub)`
+//! `s = (b_pub - k*g^x)^(a+u*x)` | | `S = (b_pub - k*g^x)^(a+u*x)`
+//! `K = H(s)` | | `K = H(s)`
+//! `M1 = H(A || B || K)` | — `M1` —> | (verify `M1`)
+//! (verify `M2`) | <— `M2` — | `M2 = H(A || M1 || K)`
+//!
+//! `||` denotes concatenation, variables and notations have the following
+//! meaning:
+//!
+//! - `I` — user identity (username)
+//! - `P` — user password
+//! - `H` — one-way hash function
+//! - `PH` — password hashing algroithm, in the RFC 5054 described as
+//! `H(s || H(I || ":" || P))`
+//! - `^` — (modular) exponentiation
+//! - `x` — user private key
+//! - `s` — salt generated by user and stored on the server
+//! - `v` — password verifier equal to `g^x` and stored on the server
+//! - `a`, `b` — secret ephemeral values (at least 256 bits in length)
+//! - `A`, `B` — Public ephemeral values
+//! - `u` — scrambling parameter
+//! - `k` — multiplier parameter (`k = H(N || g)` in SRP-6a)
+//!
+//! [1]: https://en.wikipedia.org/wiki/Secure_Remote_Password_protocol
+//! [2]: https://tools.ietf.org/html/rfc5054
+extern crate num;
+extern crate digest;
+extern crate generic_array;
+#[macro_use]
+extern crate lazy_static;
+
+#[cfg(test)]
+extern crate sha_1;
+
+mod tools;
+pub mod client;
+pub mod server;
+pub mod types;
+pub mod groups;
diff --git a/srp/src/prime.bin b/srp/src/prime.bin
new file mode 100644
index 0000000..d2109b7
--- /dev/null
+++ b/srp/src/prime.bin
@@ -0,0 +1 @@
+_ P<=èyCp^ >Hhw Bb{+2,ZuHEXrӋto 'Tw;䪗Dl'$2/ A-tcK2-懘2u7 \ No newline at end of file
diff --git a/srp/src/server.rs b/srp/src/server.rs
new file mode 100644
index 0000000..137d6b3
--- /dev/null
+++ b/srp/src/server.rs
@@ -0,0 +1,136 @@
+//! SRP server implementation
+//!
+//! # Usage
+//! First receive user's username and public value `a_pub`, retrieve from a
+//! database `UserRecord` for a given username, generate `b` (e.g. 512 bits
+//! long) and initialize SRP server instance:
+//!
+//! ```ignore
+//! use srp::groups::G_2048;
+//!
+//! let (username, a_pub) = conn.receive_handshake();
+//! let user = db.retrieve_user_record(username);
+//! let b = rng.gen_iter::<u8>().take(64).collect::<Vec<u8>>();
+//! let server = SrpServer::<Sha256>::new(&user, &a_pub, &b, &G_2048)?;
+//! ```
+//!
+//! Next send to user `b_pub` and `salt` from user record:
+//!
+//! ```ignore
+//! let b_pub = server.get_b_pub();
+//! conn.reply_to_handshake(&user.salt, b_pub);
+//! ```
+//!
+//! And finally recieve user proof, verify it and send server proof in the
+//! reply:
+//!
+//! ```ignore
+//! let user_proof = conn.receive_proof();
+//! let server_proof = server.verify(user_proof)?;
+//! conn.send_proof(server_proof);
+//! ```
+//!
+//! To get the shared secret use `get_key` method. As alternative to using
+//! `verify` method it's also possible to use this key for authentificated
+//! encryption.
+use std::marker::PhantomData;
+
+use num::{BigUint, Zero};
+use digest::Digest;
+use generic_array::GenericArray;
+
+use tools::powm;
+use types::{SrpAuthError, SrpGroup};
+
+/// Data provided by users upon registration, usually stored in the database.
+pub struct UserRecord<'a> {
+ pub username: &'a [u8],
+ pub salt: &'a [u8],
+ /// Password verifier
+ pub verifier: &'a [u8],
+}
+
+/// SRP server state
+pub struct SrpServer<D: Digest> {
+ b: BigUint,
+ a_pub: BigUint,
+ b_pub: BigUint,
+
+ key: GenericArray<u8, D::OutputSize>,
+
+ d: PhantomData<D>
+}
+
+impl< D: Digest> SrpServer< D> {
+ /// Create new server state.
+ pub fn new(user: &UserRecord, a_pub: &[u8], b: &[u8], params: &SrpGroup)
+ -> Result<Self, SrpAuthError>
+ {
+ let a_pub = BigUint::from_bytes_be(a_pub);
+ // Safeguard against malicious A
+ if &a_pub % &params.n == BigUint::zero() {
+ return Err(SrpAuthError { description: "Malicious a_pub value" })
+ }
+ let v = BigUint::from_bytes_be(user.verifier);
+ let b = BigUint::from_bytes_be(b) % &params.n;
+ let k = params.compute_k::<D>();
+ // kv + g^b
+ let interm = (k * &v) % &params.n;
+ let b_pub = (interm + &params.powm(&b)) % &params.n;
+ // H(A || B)
+ let u = {
+ let mut d = D::new();
+ d.input(&a_pub.to_bytes_be());
+ d.input(&b_pub.to_bytes_be());
+ d.result()
+ };
+ let d = Default::default();
+ //(Av^u) ^ b
+ let key = {
+ let u = BigUint::from_bytes_be(&u);
+ let t = (&a_pub * powm(&v, &u, &params.n)) % &params.n;
+ let s = powm(&t, &b, &params.n);
+ D::digest(&s.to_bytes_be())
+ };
+ Ok(Self { b, a_pub, b_pub, key, d})
+ }
+
+ /// Get private `b` value. (see `new_with_b` documentation)
+ pub fn get_b(&self) -> Vec<u8> {
+ self.b.to_bytes_be()
+ }
+
+ /// Get public `b_pub` value for sending to the user.
+ pub fn get_b_pub(&self) -> Vec<u8> {
+ self.b_pub.to_bytes_be()
+ }
+
+ /// Get shared secret between user and the server. (do not forget to verify
+ /// that keys are the same!)
+ pub fn get_key(&self) -> GenericArray<u8, D::OutputSize> {
+ self.key.clone()
+ }
+
+ /// Process user proof of having the same shared secret and compute
+ /// server proof for sending to the user.
+ pub fn verify(&self, user_proof: &[u8])
+ -> Result<GenericArray<u8, D::OutputSize>, SrpAuthError>
+ {
+ // M = H(A, B, K)
+ let mut d = D::new();
+ d.input(&self.a_pub.to_bytes_be());
+ d.input(&self.b_pub.to_bytes_be());
+ d.input(&self.key);
+
+ if user_proof == d.result().as_slice() {
+ // H(A, M, K)
+ let mut d = D::new();
+ d.input(&self.a_pub.to_bytes_be());
+ d.input(user_proof);
+ d.input(&self.key);
+ Ok(d.result())
+ } else {
+ Err(SrpAuthError { description: "Incorrect user proof" })
+ }
+ }
+}
diff --git a/srp/src/tools.rs b/srp/src/tools.rs
new file mode 100644
index 0000000..8cb6910
--- /dev/null
+++ b/srp/src/tools.rs
@@ -0,0 +1,19 @@
+use num::BigUint;
+
+pub fn powm(base: &BigUint, exp: &BigUint, modulus: &BigUint) -> BigUint {
+ let zero = BigUint::new(vec![0]);
+ let one = BigUint::new(vec![1]);
+ let two = BigUint::new(vec![2]);
+ let mut exp = exp.clone();
+ let mut result = one.clone();
+ let mut base = base % modulus;
+
+ while exp > zero {
+ if &exp % &two == one {
+ result = (result * &base) % modulus;
+ }
+ exp = exp >> 1;
+ base = (&base * &base) % modulus;
+ }
+ result
+}
diff --git a/srp/src/types.rs b/srp/src/types.rs
new file mode 100644
index 0000000..810132c
--- /dev/null
+++ b/srp/src/types.rs
@@ -0,0 +1,64 @@
+//! Additional SRP types.
+use std::{fmt, error};
+use num::BigUint;
+use tools::powm;
+use digest::Digest;
+
+/// SRP authentification error.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct SrpAuthError {
+ pub(crate) description: &'static str
+}
+
+impl fmt::Display for SrpAuthError {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "SRP authentification error")
+ }
+}
+
+impl error::Error for SrpAuthError {
+ fn description(&self) -> &str {
+ self.description
+ }
+}
+
+/// Group used for SRP computations
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct SrpGroup {
+ /// A large safe prime (N = 2q+1, where q is prime)
+ pub n: BigUint,
+ /// A generator modulo N
+ pub g: BigUint,
+}
+
+impl SrpGroup {
+ pub(crate) fn powm(&self, v: &BigUint) -> BigUint {
+ powm(&self.g, v, &self.n)
+ }
+
+ /// Compute `k` with given hash function and return SRP parameters
+ pub(crate) fn compute_k<D: Digest>(&self) -> BigUint {
+ let n = self.n.to_bytes_be();
+ let g_bytes = self.g.to_bytes_be();
+ let mut buf = vec![0u8; n.len()];
+ let l = n.len() - g_bytes.len();
+ buf[l..].copy_from_slice(&g_bytes);
+
+ let mut d = D::new();
+ d.input(&n);
+ d.input(&buf);
+ BigUint::from_bytes_be(&d.result())
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use ::groups::G_1024;
+ use sha_1::Sha1;
+
+ #[test]
+ fn test_k_1024_sha1() {
+ let k = G_1024.compute_k::<Sha1>().to_bytes_be();
+ assert_eq!(&k, include_bytes!("k_sha1_1024.bin"));
+ }
+}