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Diffstat (limited to 'lib/crypto/mldsa.c')
| -rw-r--r-- | lib/crypto/mldsa.c | 682 |
1 files changed, 682 insertions, 0 deletions
diff --git a/lib/crypto/mldsa.c b/lib/crypto/mldsa.c new file mode 100644 index 000000000000..c96fddc4e7dc --- /dev/null +++ b/lib/crypto/mldsa.c @@ -0,0 +1,682 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Support for verifying ML-DSA signatures + * + * Copyright 2025 Google LLC + */ + +#include <crypto/mldsa.h> +#include <crypto/sha3.h> +#include <kunit/visibility.h> +#include <linux/export.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/unaligned.h> +#include "fips-mldsa.h" + +#define Q 8380417 /* The prime q = 2^23 - 2^13 + 1 */ +#define QINV_MOD_2_32 58728449 /* Multiplicative inverse of q mod 2^32 */ +#define N 256 /* Number of components per ring element */ +#define D 13 /* Number of bits dropped from the public key vector t */ +#define RHO_LEN 32 /* Length of the public random seed in bytes */ +#define MAX_W1_ENCODED_LEN 192 /* Max encoded length of one element of w'_1 */ + +/* + * The zetas array in Montgomery form, i.e. with extra factor of 2^32. + * Reference: FIPS 204 Section 7.5 "NTT and NTT^-1" + * Generated by the following Python code: + * q=8380417; [a%q - q*(a%q > q//2) for a in [1753**(int(f'{i:08b}'[::-1], 2)) << 32 for i in range(256)]] + */ +static const s32 zetas_times_2_32[N] = { + -4186625, 25847, -2608894, -518909, 237124, -777960, -876248, + 466468, 1826347, 2353451, -359251, -2091905, 3119733, -2884855, + 3111497, 2680103, 2725464, 1024112, -1079900, 3585928, -549488, + -1119584, 2619752, -2108549, -2118186, -3859737, -1399561, -3277672, + 1757237, -19422, 4010497, 280005, 2706023, 95776, 3077325, + 3530437, -1661693, -3592148, -2537516, 3915439, -3861115, -3043716, + 3574422, -2867647, 3539968, -300467, 2348700, -539299, -1699267, + -1643818, 3505694, -3821735, 3507263, -2140649, -1600420, 3699596, + 811944, 531354, 954230, 3881043, 3900724, -2556880, 2071892, + -2797779, -3930395, -1528703, -3677745, -3041255, -1452451, 3475950, + 2176455, -1585221, -1257611, 1939314, -4083598, -1000202, -3190144, + -3157330, -3632928, 126922, 3412210, -983419, 2147896, 2715295, + -2967645, -3693493, -411027, -2477047, -671102, -1228525, -22981, + -1308169, -381987, 1349076, 1852771, -1430430, -3343383, 264944, + 508951, 3097992, 44288, -1100098, 904516, 3958618, -3724342, + -8578, 1653064, -3249728, 2389356, -210977, 759969, -1316856, + 189548, -3553272, 3159746, -1851402, -2409325, -177440, 1315589, + 1341330, 1285669, -1584928, -812732, -1439742, -3019102, -3881060, + -3628969, 3839961, 2091667, 3407706, 2316500, 3817976, -3342478, + 2244091, -2446433, -3562462, 266997, 2434439, -1235728, 3513181, + -3520352, -3759364, -1197226, -3193378, 900702, 1859098, 909542, + 819034, 495491, -1613174, -43260, -522500, -655327, -3122442, + 2031748, 3207046, -3556995, -525098, -768622, -3595838, 342297, + 286988, -2437823, 4108315, 3437287, -3342277, 1735879, 203044, + 2842341, 2691481, -2590150, 1265009, 4055324, 1247620, 2486353, + 1595974, -3767016, 1250494, 2635921, -3548272, -2994039, 1869119, + 1903435, -1050970, -1333058, 1237275, -3318210, -1430225, -451100, + 1312455, 3306115, -1962642, -1279661, 1917081, -2546312, -1374803, + 1500165, 777191, 2235880, 3406031, -542412, -2831860, -1671176, + -1846953, -2584293, -3724270, 594136, -3776993, -2013608, 2432395, + 2454455, -164721, 1957272, 3369112, 185531, -1207385, -3183426, + 162844, 1616392, 3014001, 810149, 1652634, -3694233, -1799107, + -3038916, 3523897, 3866901, 269760, 2213111, -975884, 1717735, + 472078, -426683, 1723600, -1803090, 1910376, -1667432, -1104333, + -260646, -3833893, -2939036, -2235985, -420899, -2286327, 183443, + -976891, 1612842, -3545687, -554416, 3919660, -48306, -1362209, + 3937738, 1400424, -846154, 1976782 +}; + +/* Reference: FIPS 204 Section 4 "Parameter Sets" */ +static const struct mldsa_parameter_set { + u8 k; /* num rows in the matrix A */ + u8 l; /* num columns in the matrix A */ + u8 ctilde_len; /* length of commitment hash ctilde in bytes; lambda/4 */ + u8 omega; /* max num of 1's in the hint vector h */ + u8 tau; /* num of +-1's in challenge c */ + u8 beta; /* tau times eta */ + u16 pk_len; /* length of public keys in bytes */ + u16 sig_len; /* length of signatures in bytes */ + s32 gamma1; /* coefficient range of y */ +} mldsa_parameter_sets[] = { + [MLDSA44] = { + .k = 4, + .l = 4, + .ctilde_len = 32, + .omega = 80, + .tau = 39, + .beta = 78, + .pk_len = MLDSA44_PUBLIC_KEY_SIZE, + .sig_len = MLDSA44_SIGNATURE_SIZE, + .gamma1 = 1 << 17, + }, + [MLDSA65] = { + .k = 6, + .l = 5, + .ctilde_len = 48, + .omega = 55, + .tau = 49, + .beta = 196, + .pk_len = MLDSA65_PUBLIC_KEY_SIZE, + .sig_len = MLDSA65_SIGNATURE_SIZE, + .gamma1 = 1 << 19, + }, + [MLDSA87] = { + .k = 8, + .l = 7, + .ctilde_len = 64, + .omega = 75, + .tau = 60, + .beta = 120, + .pk_len = MLDSA87_PUBLIC_KEY_SIZE, + .sig_len = MLDSA87_SIGNATURE_SIZE, + .gamma1 = 1 << 19, + }, +}; + +/* + * An element of the ring R_q (normal form) or the ring T_q (NTT form). It + * consists of N integers mod q: either the polynomial coefficients of the R_q + * element or the components of the T_q element. In either case, whether they + * are fully reduced to [0, q - 1] varies in the different parts of the code. + */ +struct mldsa_ring_elem { + s32 x[N]; +}; + +struct mldsa_verification_workspace { + /* SHAKE context for computing c, mu, and ctildeprime */ + struct shake_ctx shake; + /* The fields in this union are used in their order of declaration. */ + union { + /* The hash of the public key */ + u8 tr[64]; + /* The message representative mu */ + u8 mu[64]; + /* Temporary space for rej_ntt_poly() */ + u8 block[SHAKE128_BLOCK_SIZE + 1]; + /* Encoded element of w'_1 */ + u8 w1_encoded[MAX_W1_ENCODED_LEN]; + /* The commitment hash. Real length is params->ctilde_len */ + u8 ctildeprime[64]; + }; + /* SHAKE context for generating elements of the matrix A */ + struct shake_ctx a_shake; + /* + * An element of the matrix A generated from the public seed, or an + * element of the vector t_1 decoded from the public key and pre-scaled + * by 2^d. Both are in NTT form. To reduce memory usage, we generate + * or decode these elements only as needed. + */ + union { + struct mldsa_ring_elem a; + struct mldsa_ring_elem t1_scaled; + }; + /* The challenge c, generated from ctilde */ + struct mldsa_ring_elem c; + /* A temporary element used during calculations */ + struct mldsa_ring_elem tmp; + + /* The following fields are variable-length: */ + + /* The signer's response vector */ + struct mldsa_ring_elem z[/* l */]; + + /* The signer's hint vector */ + /* u8 h[k * N]; */ +}; + +/* + * Compute a * b * 2^-32 mod q. a * b must be in the range [-2^31 * q, 2^31 * q + * - 1] before reduction. The return value is in the range [-q + 1, q - 1]. + * + * To reduce mod q efficiently, this uses Montgomery reduction with R=2^32. + * That's where the factor of 2^-32 comes from. The caller must include a + * factor of 2^32 at some point to compensate for that. + * + * To keep the input and output ranges very close to symmetric, this + * specifically does a "signed" Montgomery reduction. That is, when computing + * d = c * q^-1 mod 2^32, this chooses a representative in [S32_MIN, S32_MAX] + * rather than [0, U32_MAX], i.e. s32 rather than u32. This matters in the + * wider multiplication d * Q when d keeps its value via sign extension. + * + * Reference: FIPS 204 Appendix A "Montgomery Multiplication". But, it doesn't + * explain it properly: it has an off-by-one error in the upper end of the input + * range, it doesn't clarify that the signed version should be used, and it + * gives an unnecessarily large output range. A better citation is perhaps the + * Dilithium reference code, which functionally matches the below code and + * merely has the (benign) off-by-one error in its documentation. + */ +static inline s32 Zq_mult(s32 a, s32 b) +{ + /* Compute the unreduced product c. */ + s64 c = (s64)a * b; + + /* + * Compute d = c * q^-1 mod 2^32. Generate a signed result, as + * explained above, but do the actual multiplication using an unsigned + * type to avoid signed integer overflow which is undefined behavior. + */ + s32 d = (u32)c * QINV_MOD_2_32; + + /* + * Compute e = c - d * q. This makes the low 32 bits zero, since + * c - (c * q^-1) * q mod 2^32 + * = c - c * (q^-1 * q) mod 2^32 + * = c - c * 1 mod 2^32 + * = c - c mod 2^32 + * = 0 mod 2^32 + */ + s64 e = c - (s64)d * Q; + + /* Finally, return e * 2^-32. */ + return e >> 32; +} + +/* + * Convert @w to its number-theoretically-transformed representation in-place. + * Reference: FIPS 204 Algorithm 41, NTT + * + * To prevent intermediate overflows, all input coefficients must have absolute + * value < q. All output components have absolute value < 9*q. + */ +static void ntt(struct mldsa_ring_elem *w) +{ + int m = 0; /* index in zetas_times_2_32 */ + + for (int len = 128; len >= 1; len /= 2) { + for (int start = 0; start < 256; start += 2 * len) { + const s32 z = zetas_times_2_32[++m]; + + for (int j = start; j < start + len; j++) { + s32 t = Zq_mult(z, w->x[j + len]); + + w->x[j + len] = w->x[j] - t; + w->x[j] += t; + } + } + } +} + +/* + * Convert @w from its number-theoretically-transformed representation in-place. + * Reference: FIPS 204 Algorithm 42, NTT^-1 + * + * This also multiplies the coefficients by 2^32, undoing an extra factor of + * 2^-32 introduced earlier, and reduces the coefficients to [0, q - 1]. + */ +static void invntt_and_mul_2_32(struct mldsa_ring_elem *w) +{ + int m = 256; /* index in zetas_times_2_32 */ + + /* Prevent intermediate overflows. */ + for (int j = 0; j < 256; j++) + w->x[j] %= Q; + + for (int len = 1; len < 256; len *= 2) { + for (int start = 0; start < 256; start += 2 * len) { + const s32 z = -zetas_times_2_32[--m]; + + for (int j = start; j < start + len; j++) { + s32 t = w->x[j]; + + w->x[j] = t + w->x[j + len]; + w->x[j + len] = Zq_mult(z, t - w->x[j + len]); + } + } + } + /* + * Multiply by 2^32 * 256^-1. 2^32 cancels the factor of 2^-32 from + * earlier Montgomery multiplications. 256^-1 is for NTT^-1. This + * itself uses Montgomery multiplication, so *another* 2^32 is needed. + * Thus the actual multiplicand is 2^32 * 2^32 * 256^-1 mod q = 41978. + * + * Finally, also reduce from [-q + 1, q - 1] to [0, q - 1]. + */ + for (int j = 0; j < 256; j++) { + w->x[j] = Zq_mult(w->x[j], 41978); + w->x[j] += (w->x[j] >> 31) & Q; + } +} + +/* + * Decode an element of t_1, i.e. the high d bits of t = A*s_1 + s_2. + * Reference: FIPS 204 Algorithm 23, pkDecode. + * Also multiply it by 2^d and convert it to NTT form. + */ +static const u8 *decode_t1_elem(struct mldsa_ring_elem *out, + const u8 *t1_encoded) +{ + for (int j = 0; j < N; j += 4, t1_encoded += 5) { + u32 v = get_unaligned_le32(t1_encoded); + + out->x[j + 0] = ((v >> 0) & 0x3ff) << D; + out->x[j + 1] = ((v >> 10) & 0x3ff) << D; + out->x[j + 2] = ((v >> 20) & 0x3ff) << D; + out->x[j + 3] = ((v >> 30) | (t1_encoded[4] << 2)) << D; + static_assert(0x3ff << D < Q); /* All coefficients < q. */ + } + ntt(out); + return t1_encoded; /* Return updated pointer. */ +} + +/* + * Decode the signer's response vector 'z' from the signature. + * Reference: FIPS 204 Algorithm 27, sigDecode. + * + * This also validates that the coefficients of z are in range, corresponding + * the infinity norm check at the end of Algorithm 8, ML-DSA.Verify_internal. + * + * Finally, this also converts z to NTT form. + */ +static bool decode_z(struct mldsa_ring_elem z[/* l */], int l, s32 gamma1, + int beta, const u8 **sig_ptr) +{ + const u8 *sig = *sig_ptr; + + for (int i = 0; i < l; i++) { + if (l == 4) { /* ML-DSA-44? */ + /* 18-bit coefficients: decode 4 from 9 bytes. */ + for (int j = 0; j < N; j += 4, sig += 9) { + u64 v = get_unaligned_le64(sig); + + z[i].x[j + 0] = (v >> 0) & 0x3ffff; + z[i].x[j + 1] = (v >> 18) & 0x3ffff; + z[i].x[j + 2] = (v >> 36) & 0x3ffff; + z[i].x[j + 3] = (v >> 54) | (sig[8] << 10); + } + } else { + /* 20-bit coefficients: decode 4 from 10 bytes. */ + for (int j = 0; j < N; j += 4, sig += 10) { + u64 v = get_unaligned_le64(sig); + + z[i].x[j + 0] = (v >> 0) & 0xfffff; + z[i].x[j + 1] = (v >> 20) & 0xfffff; + z[i].x[j + 2] = (v >> 40) & 0xfffff; + z[i].x[j + 3] = + (v >> 60) | + (get_unaligned_le16(&sig[8]) << 4); + } + } + for (int j = 0; j < N; j++) { + z[i].x[j] = gamma1 - z[i].x[j]; + if (z[i].x[j] <= -(gamma1 - beta) || + z[i].x[j] >= gamma1 - beta) + return false; + } + ntt(&z[i]); + } + *sig_ptr = sig; /* Return updated pointer. */ + return true; +} + +/* + * Decode the signer's hint vector 'h' from the signature. + * Reference: FIPS 204 Algorithm 21, HintBitUnpack + * + * Note that there are several ways in which the hint vector can be malformed. + */ +static bool decode_hint_vector(u8 h[/* k * N */], int k, int omega, const u8 *y) +{ + int index = 0; + + memset(h, 0, k * N); + for (int i = 0; i < k; i++) { + int count = y[omega + i]; /* num 1's in elems 0 through i */ + int prev = -1; + + /* Cumulative count mustn't decrease or exceed omega. */ + if (count < index || count > omega) + return false; + for (; index < count; index++) { + if (prev >= y[index]) /* Coefficients out of order? */ + return false; + prev = y[index]; + h[i * N + y[index]] = 1; + } + } + return mem_is_zero(&y[index], omega - index); +} + +/* + * Expand @seed into an element of R_q @c with coefficients in {-1, 0, 1}, + * exactly @tau of them nonzero. Reference: FIPS 204 Algorithm 29, SampleInBall + */ +static void sample_in_ball(struct mldsa_ring_elem *c, const u8 *seed, + size_t seed_len, int tau, struct shake_ctx *shake) +{ + u64 signs; + u8 j; + + shake256_init(shake); + shake_update(shake, seed, seed_len); + shake_squeeze(shake, (u8 *)&signs, sizeof(signs)); + le64_to_cpus(&signs); + *c = (struct mldsa_ring_elem){}; + for (int i = N - tau; i < N; i++, signs >>= 1) { + do { + shake_squeeze(shake, &j, 1); + } while (j > i); + c->x[i] = c->x[j]; + c->x[j] = 1 - 2 * (s32)(signs & 1); + } +} + +/* + * Expand the public seed @rho and @row_and_column into an element of T_q @out. + * Reference: FIPS 204 Algorithm 30, RejNTTPoly + * + * @shake and @block are temporary space used by the expansion. @block has + * space for one SHAKE128 block, plus an extra byte to allow reading a u32 from + * the final 3-byte group without reading out-of-bounds. + */ +static void rej_ntt_poly(struct mldsa_ring_elem *out, const u8 rho[RHO_LEN], + __le16 row_and_column, struct shake_ctx *shake, + u8 block[SHAKE128_BLOCK_SIZE + 1]) +{ + shake128_init(shake); + shake_update(shake, rho, RHO_LEN); + shake_update(shake, (u8 *)&row_and_column, sizeof(row_and_column)); + for (int i = 0; i < N;) { + shake_squeeze(shake, block, SHAKE128_BLOCK_SIZE); + block[SHAKE128_BLOCK_SIZE] = 0; /* for KMSAN */ + static_assert(SHAKE128_BLOCK_SIZE % 3 == 0); + for (int j = 0; j < SHAKE128_BLOCK_SIZE && i < N; j += 3) { + u32 x = get_unaligned_le32(&block[j]) & 0x7fffff; + + if (x < Q) /* Ignore values >= q. */ + out->x[i++] = x; + } + } +} + +/* + * Return the HighBits of r adjusted according to hint h + * Reference: FIPS 204 Algorithm 40, UseHint + * + * This is needed because of the public key compression in ML-DSA. + * + * h is either 0 or 1, r is in [0, q - 1], and gamma2 is either (q - 1) / 88 or + * (q - 1) / 32. Except when invoked via the unit test interface, gamma2 is a + * compile-time constant, so compilers will optimize the code accordingly. + */ +static __always_inline s32 use_hint(u8 h, s32 r, const s32 gamma2) +{ + const s32 m = (Q - 1) / (2 * gamma2); /* 44 or 16, compile-time const */ + s32 r1; + + /* + * Handle the special case where r - (r mod+- (2 * gamma2)) == q - 1, + * i.e. r >= q - gamma2. This is also exactly where the computation of + * r1 below would produce 'm' and would need a correction. + */ + if (r >= Q - gamma2) + return h == 0 ? 0 : m - 1; + + /* + * Compute the (non-hint-adjusted) HighBits r1 as: + * + * r1 = (r - (r mod+- (2 * gamma2))) / (2 * gamma2) + * = floor((r + gamma2 - 1) / (2 * gamma2)) + * + * Note that when '2 * gamma2' is a compile-time constant, compilers + * optimize the division to a reciprocal multiplication and shift. + */ + r1 = (u32)(r + gamma2 - 1) / (2 * gamma2); + + /* + * Return the HighBits r1: + * + 0 if the hint is 0; + * + 1 (mod m) if the hint is 1 and the LowBits are positive; + * - 1 (mod m) if the hint is 1 and the LowBits are negative or 0. + * + * r1 is in (and remains in) [0, m - 1]. Note that when 'm' is a + * compile-time constant, compilers optimize the '% m' accordingly. + */ + if (h == 0) + return r1; + if (r > r1 * (2 * gamma2)) + return (u32)(r1 + 1) % m; + return (u32)(r1 + m - 1) % m; +} + +static __always_inline void use_hint_elem(struct mldsa_ring_elem *w, + const u8 h[N], const s32 gamma2) +{ + for (int j = 0; j < N; j++) + w->x[j] = use_hint(h[j], w->x[j], gamma2); +} + +#if IS_ENABLED(CONFIG_CRYPTO_LIB_MLDSA_KUNIT_TEST) +/* Allow the __always_inline function use_hint() to be unit-tested. */ +s32 mldsa_use_hint(u8 h, s32 r, s32 gamma2) +{ + return use_hint(h, r, gamma2); +} +EXPORT_SYMBOL_IF_KUNIT(mldsa_use_hint); +#endif + +/* + * Encode one element of the commitment vector w'_1 into a byte string. + * Reference: FIPS 204 Algorithm 28, w1Encode. + * Return the number of bytes used: 192 for ML-DSA-44 and 128 for the others. + */ +static size_t encode_w1(u8 out[MAX_W1_ENCODED_LEN], + const struct mldsa_ring_elem *w1, int k) +{ + size_t pos = 0; + + static_assert(N * 6 / 8 == MAX_W1_ENCODED_LEN); + if (k == 4) { /* ML-DSA-44? */ + /* 6 bits per coefficient. Pack 4 at a time. */ + for (int j = 0; j < N; j += 4) { + u32 v = (w1->x[j + 0] << 0) | (w1->x[j + 1] << 6) | + (w1->x[j + 2] << 12) | (w1->x[j + 3] << 18); + out[pos++] = v >> 0; + out[pos++] = v >> 8; + out[pos++] = v >> 16; + } + } else { + /* 4 bits per coefficient. Pack 2 at a time. */ + for (int j = 0; j < N; j += 2) + out[pos++] = w1->x[j] | (w1->x[j + 1] << 4); + } + return pos; +} + +int mldsa_verify(enum mldsa_alg alg, const u8 *sig, size_t sig_len, + const u8 *msg, size_t msg_len, const u8 *pk, size_t pk_len) +{ + const struct mldsa_parameter_set *params = &mldsa_parameter_sets[alg]; + const int k = params->k, l = params->l; + /* For now this just does pure ML-DSA with an empty context string. */ + static const u8 msg_prefix[2] = { /* dom_sep= */ 0, /* ctx_len= */ 0 }; + const u8 *ctilde; /* The signer's commitment hash */ + const u8 *t1_encoded = &pk[RHO_LEN]; /* Next encoded element of t_1 */ + u8 *h; /* The signer's hint vector, length k * N */ + size_t w1_enc_len; + + /* Validate the public key and signature lengths. */ + if (pk_len != params->pk_len || sig_len != params->sig_len) + return -EBADMSG; + + /* + * Allocate the workspace, including variable-length fields. Its size + * depends only on the ML-DSA parameter set, not the other inputs. + * + * For freeing it, use kfree_sensitive() rather than kfree(). This is + * mainly to comply with FIPS 204 Section 3.6.3 "Intermediate Values". + * In reality it's a bit gratuitous, as this is a public key operation. + */ + struct mldsa_verification_workspace *ws __free(kfree_sensitive) = + kmalloc(sizeof(*ws) + (l * sizeof(ws->z[0])) + (k * N), + GFP_KERNEL); + if (!ws) + return -ENOMEM; + h = (u8 *)&ws->z[l]; + + /* Decode the signature. Reference: FIPS 204 Algorithm 27, sigDecode */ + ctilde = sig; + sig += params->ctilde_len; + if (!decode_z(ws->z, l, params->gamma1, params->beta, &sig)) + return -EBADMSG; + if (!decode_hint_vector(h, k, params->omega, sig)) + return -EBADMSG; + + /* Recreate the challenge c from the signer's commitment hash. */ + sample_in_ball(&ws->c, ctilde, params->ctilde_len, params->tau, + &ws->shake); + ntt(&ws->c); + + /* Compute the message representative mu. */ + shake256(pk, pk_len, ws->tr, sizeof(ws->tr)); + shake256_init(&ws->shake); + shake_update(&ws->shake, ws->tr, sizeof(ws->tr)); + shake_update(&ws->shake, msg_prefix, sizeof(msg_prefix)); + shake_update(&ws->shake, msg, msg_len); + shake_squeeze(&ws->shake, ws->mu, sizeof(ws->mu)); + + /* Start computing ctildeprime = H(mu || w1Encode(w'_1)). */ + shake256_init(&ws->shake); + shake_update(&ws->shake, ws->mu, sizeof(ws->mu)); + + /* + * Compute the commitment w'_1 from A, z, c, t_1, and h. + * + * The computation is the same for each of the k rows. Just do each row + * before moving on to the next, resulting in only one loop over k. + */ + for (int i = 0; i < k; i++) { + /* + * tmp = NTT(A) * NTT(z) * 2^-32 + * To reduce memory use, generate each element of NTT(A) + * on-demand. Note that each element is used only once. + */ + ws->tmp = (struct mldsa_ring_elem){}; + for (int j = 0; j < l; j++) { + rej_ntt_poly(&ws->a, pk /* rho is first field of pk */, + cpu_to_le16((i << 8) | j), &ws->a_shake, + ws->block); + for (int n = 0; n < N; n++) + ws->tmp.x[n] += + Zq_mult(ws->a.x[n], ws->z[j].x[n]); + } + /* All components of tmp now have abs value < l*q. */ + + /* Decode the next element of t_1. */ + t1_encoded = decode_t1_elem(&ws->t1_scaled, t1_encoded); + + /* + * tmp -= NTT(c) * NTT(t_1 * 2^d) * 2^-32 + * + * Taking a conservative bound for the output of ntt(), the + * multiplicands can have absolute value up to 9*q. That + * corresponds to a product with absolute value 81*q^2. That is + * within the limits of Zq_mult() which needs < ~256*q^2. + */ + for (int j = 0; j < N; j++) + ws->tmp.x[j] -= Zq_mult(ws->c.x[j], ws->t1_scaled.x[j]); + /* All components of tmp now have abs value < (l+1)*q. */ + + /* tmp = w'_Approx = NTT^-1(tmp) * 2^32 */ + invntt_and_mul_2_32(&ws->tmp); + /* All coefficients of tmp are now in [0, q - 1]. */ + + /* + * tmp = w'_1 = UseHint(h, w'_Approx) + * For efficiency, set gamma2 to a compile-time constant. + */ + if (k == 4) + use_hint_elem(&ws->tmp, &h[i * N], (Q - 1) / 88); + else + use_hint_elem(&ws->tmp, &h[i * N], (Q - 1) / 32); + + /* Encode and hash the next element of w'_1. */ + w1_enc_len = encode_w1(ws->w1_encoded, &ws->tmp, k); + shake_update(&ws->shake, ws->w1_encoded, w1_enc_len); + } + + /* Finish computing ctildeprime. */ + shake_squeeze(&ws->shake, ws->ctildeprime, params->ctilde_len); + + /* Verify that ctilde == ctildeprime. */ + if (memcmp(ws->ctildeprime, ctilde, params->ctilde_len) != 0) + return -EKEYREJECTED; + /* ||z||_infinity < gamma1 - beta was already checked in decode_z(). */ + return 0; +} +EXPORT_SYMBOL_GPL(mldsa_verify); + +#ifdef CONFIG_CRYPTO_FIPS +static int __init mldsa_mod_init(void) +{ + if (fips_enabled) { + /* + * FIPS cryptographic algorithm self-test. As per the FIPS + * Implementation Guidance, testing any ML-DSA parameter set + * satisfies the test requirement for all of them, and only a + * positive test is required. + */ + int err = mldsa_verify(MLDSA65, fips_test_mldsa65_signature, + sizeof(fips_test_mldsa65_signature), + fips_test_mldsa65_message, + sizeof(fips_test_mldsa65_message), + fips_test_mldsa65_public_key, + sizeof(fips_test_mldsa65_public_key)); + if (err) + panic("mldsa: FIPS self-test failed; err=%pe\n", + ERR_PTR(err)); + } + return 0; +} +subsys_initcall(mldsa_mod_init); + +static void __exit mldsa_mod_exit(void) +{ +} +module_exit(mldsa_mod_exit); +#endif /* CONFIG_CRYPTO_FIPS */ + +MODULE_DESCRIPTION("ML-DSA signature verification"); +MODULE_LICENSE("GPL"); |