1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

//! Digital Signature Algorithm (DSA) public keys.

use crate::{Error, Mpint, Result};
use core::hash::{Hash, Hasher};
use encoding::{CheckedSum, Decode, Encode, Reader, Writer};

/// Digital Signature Algorithm (DSA) public key.
///
/// Described in [FIPS 186-4 § 4.1](https://csrc.nist.gov/publications/detail/fips/186/4/final).
#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub struct DsaPublicKey {
    /// Prime modulus.
    p: Mpint,

    /// Prime divisor of `p - 1`.
    q: Mpint,

    /// Generator of a subgroup of order `q` in the multiplicative group `GF(p)`, such that
    /// `1 < g < p`.
    g: Mpint,

    /// The public key, where `y = gˣ mod p`.
    y: Mpint,
}

impl DsaPublicKey {
    /// Create a new [`DsaPublicKey`] with the following components:
    ///
    /// - `p`: prime modulus.
    /// - `q`: prime divisor of `p - 1`.
    /// - `g`: generator of a subgroup of order `q` in the multiplicative group `GF(p)`, such
    ///   that `1 < g < p`.
    /// - `y`: the public key, where `y = gˣ mod p`.
    pub fn new(p: Mpint, q: Mpint, g: Mpint, y: Mpint) -> Result<Self> {
        if p.is_positive() && q.is_positive() && g.is_positive() && y.is_positive() {
            Ok(Self { p, q, g, y })
        } else {
            Err(Error::FormatEncoding)
        }
    }

    /// Prime modulus.
    pub fn p(&self) -> &Mpint {
        &self.p
    }

    /// Prime divisor of `p - 1`.
    pub fn q(&self) -> &Mpint {
        &self.q
    }

    /// Generator of a subgroup of order `q` in the multiplicative group `GF(p)`, such that
    /// `1 < g < p`.
    pub fn g(&self) -> &Mpint {
        &self.g
    }

    /// The public key, where `y = gˣ mod p`.
    pub fn y(&self) -> &Mpint {
        &self.y
    }
}

impl Decode for DsaPublicKey {
    type Error = Error;

    fn decode(reader: &mut impl Reader) -> Result<Self> {
        let p = Mpint::decode(reader)?;
        let q = Mpint::decode(reader)?;
        let g = Mpint::decode(reader)?;
        let y = Mpint::decode(reader)?;
        Self::new(p, q, g, y)
    }
}

impl Encode for DsaPublicKey {
    fn encoded_len(&self) -> encoding::Result<usize> {
        [
            self.p.encoded_len()?,
            self.q.encoded_len()?,
            self.g.encoded_len()?,
            self.y.encoded_len()?,
        ]
        .checked_sum()
    }

    fn encode(&self, writer: &mut impl Writer) -> encoding::Result<()> {
        self.p.encode(writer)?;
        self.q.encode(writer)?;
        self.g.encode(writer)?;
        self.y.encode(writer)
    }
}

impl Hash for DsaPublicKey {
    #[inline]
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.p.as_bytes().hash(state);
        self.q.as_bytes().hash(state);
        self.g.as_bytes().hash(state);
        self.y.as_bytes().hash(state);
    }
}

#[cfg(feature = "dsa")]
impl TryFrom<DsaPublicKey> for dsa::VerifyingKey {
    type Error = Error;

    fn try_from(key: DsaPublicKey) -> Result<dsa::VerifyingKey> {
        dsa::VerifyingKey::try_from(&key)
    }
}

#[cfg(feature = "dsa")]
impl TryFrom<&DsaPublicKey> for dsa::VerifyingKey {
    type Error = Error;

    fn try_from(key: &DsaPublicKey) -> Result<dsa::VerifyingKey> {
        let components = dsa::Components::from_components(
            dsa::BigUint::try_from(&key.p)?,
            dsa::BigUint::try_from(&key.q)?,
            dsa::BigUint::try_from(&key.g)?,
        )?;

        dsa::VerifyingKey::from_components(components, dsa::BigUint::try_from(&key.y)?)
            .map_err(|_| Error::Crypto)
    }
}

#[cfg(feature = "dsa")]
impl TryFrom<dsa::VerifyingKey> for DsaPublicKey {
    type Error = Error;

    fn try_from(key: dsa::VerifyingKey) -> Result<DsaPublicKey> {
        DsaPublicKey::try_from(&key)
    }
}

#[cfg(feature = "dsa")]
impl TryFrom<&dsa::VerifyingKey> for DsaPublicKey {
    type Error = Error;

    fn try_from(key: &dsa::VerifyingKey) -> Result<DsaPublicKey> {
        Ok(DsaPublicKey {
            p: key.components().p().try_into()?,
            q: key.components().q().try_into()?,
            g: key.components().g().try_into()?,
            y: key.y().try_into()?,
        })
    }
}