ring/ec/curve25519/ed25519/
verification.rs

1// Copyright 2015-2016 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15//! EdDSA Signatures.
16
17use super::{super::ops::*, eddsa_digest};
18use crate::{error, sealed, signature};
19use core::convert::TryInto;
20
21/// Parameters for EdDSA signing and verification.
22pub struct EdDSAParameters;
23
24impl core::fmt::Debug for EdDSAParameters {
25    fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
26        write!(f, "ring::signature::ED25519")
27    }
28}
29
30/// Verification of [Ed25519] signatures.
31///
32/// Ed25519 uses SHA-512 as the digest algorithm.
33///
34/// [Ed25519]: https://ed25519.cr.yp.to/
35pub static ED25519: EdDSAParameters = EdDSAParameters {};
36
37impl signature::VerificationAlgorithm for EdDSAParameters {
38    fn verify(
39        &self,
40        public_key: untrusted::Input,
41        msg: untrusted::Input,
42        signature: untrusted::Input,
43    ) -> Result<(), error::Unspecified> {
44        let public_key: &[u8; ELEM_LEN] = public_key.as_slice_less_safe().try_into()?;
45        let (signature_r, signature_s) = signature.read_all(error::Unspecified, |input| {
46            let signature_r: &[u8; ELEM_LEN] = input
47                .read_bytes(ELEM_LEN)?
48                .as_slice_less_safe()
49                .try_into()?;
50            let signature_s: &[u8; SCALAR_LEN] = input
51                .read_bytes(SCALAR_LEN)?
52                .as_slice_less_safe()
53                .try_into()?;
54            Ok((signature_r, signature_s))
55        })?;
56
57        let signature_s = Scalar::from_bytes_checked(*signature_s)?;
58
59        let mut a = ExtPoint::from_encoded_point_vartime(public_key)?;
60        a.invert_vartime();
61
62        let h_digest = eddsa_digest(signature_r, public_key, msg.as_slice_less_safe());
63        let h = Scalar::from_sha512_digest_reduced(h_digest);
64
65        let mut r = Point::new_at_infinity();
66        unsafe { GFp_x25519_ge_double_scalarmult_vartime(&mut r, &h, &a, &signature_s) };
67        let r_check = r.into_encoded_point();
68        if *signature_r != r_check {
69            return Err(error::Unspecified);
70        }
71        Ok(())
72    }
73}
74
75impl sealed::Sealed for EdDSAParameters {}
76
77extern "C" {
78    fn GFp_x25519_ge_double_scalarmult_vartime(
79        r: &mut Point,
80        a_coeff: &Scalar,
81        a: &ExtPoint,
82        b_coeff: &Scalar,
83    );
84}
ring/ec/curve25519/ed25519/verification.rs

ring/ec/curve25519/ed25519/
verification.rs
