gsw_rs/
params.rs

1//! LWE/GSW parameter definitions.
2//!
3//! Parameters are chosen for correctness with conservative security levels.
4//! In production, use lattice estimators for proper security parameter selection.
5
6/// Security level in bits.
7#[derive(Clone, Copy, Debug, PartialEq, Eq)]
8pub enum SecurityLevel {
9    /// Toy parameters for testing (~32-bit security)
10    Toy,
11    /// Low security (~64-bit)
12    Low,
13    /// Medium security (~128-bit)
14    Medium,
15}
16
17/// LWE/GSW instance parameters.
18#[derive(Clone, Debug)]
19pub struct Params {
20    /// Modulus q (must be power of 2 for gadget)
21    pub q: u64,
22    /// Lattice dimension n
23    pub n: usize,
24    /// Number of bits to represent q: l = log2(q)
25    pub l: usize,
26    /// N = (n+1) * l - dimension of expanded gadget space
27    pub n_expanded: usize,
28    /// Number of LWE samples for public key (columns of A)
29    pub m: usize,
30    /// Error bound B for discrete uniform error distribution [-B, B]
31    pub error_bound: i64,
32}
33
34impl Params {
35    /// Create parameters for the given security level.
36    ///
37    /// Parameters are chosen so that correctness never fails:
38    /// - Error growth: mult multiplies error by ~N=(n+1)*l, add doubles it
39    /// - Requirement: N * sqrt(m) * B ≪ q/4 for one multiplication
40    pub fn new(level: SecurityLevel) -> Self {
41        let mut p = match level {
42            SecurityLevel::Toy => Self {
43                q: 1 << 20,   // 1M - margin for correctness
44                n: 8,
45                m: 256,
46                error_bound: 1,
47                l: 0,
48                n_expanded: 0,
49            },
50            SecurityLevel::Low => Self {
51                q: 1 << 24,
52                n: 24,
53                m: 384,
54                error_bound: 2,
55                l: 0,
56                n_expanded: 0,
57            },
58            SecurityLevel::Medium => Self {
59                q: 1 << 26,
60                n: 48,
61                m: 768,
62                error_bound: 4,
63                l: 0,
64                n_expanded: 0,
65            },
66        };
67        p.with_derived();
68        p
69    }
70
71    /// Create toy parameters for quick testing.
72    pub fn toy() -> Self {
73        Self::new(SecurityLevel::Toy)
74    }
75
76    fn with_derived(&mut self) {
77        self.l = (self.q as f64).log2() as usize;
78        self.n_expanded = (self.n + 1) * self.l;
79    }
80}
gsw_rs/params.rs

gsw_rs/
params.rs
