diff options
Diffstat (limited to 'lib/mpi/mpi-mod.c')
| -rw-r--r-- | lib/mpi/mpi-mod.c | 157 |
1 files changed, 0 insertions, 157 deletions
diff --git a/lib/mpi/mpi-mod.c b/lib/mpi/mpi-mod.c deleted file mode 100644 index 54fcc01564d9..000000000000 --- a/lib/mpi/mpi-mod.c +++ /dev/null @@ -1,157 +0,0 @@ -/* mpi-mod.c - Modular reduction - * Copyright (C) 1998, 1999, 2001, 2002, 2003, - * 2007 Free Software Foundation, Inc. - * - * This file is part of Libgcrypt. - */ - - -#include "mpi-internal.h" -#include "longlong.h" - -/* Context used with Barrett reduction. */ -struct barrett_ctx_s { - MPI m; /* The modulus - may not be modified. */ - int m_copied; /* If true, M needs to be released. */ - int k; - MPI y; - MPI r1; /* Helper MPI. */ - MPI r2; /* Helper MPI. */ - MPI r3; /* Helper MPI allocated on demand. */ -}; - - - -void mpi_mod(MPI rem, MPI dividend, MPI divisor) -{ - mpi_fdiv_r(rem, dividend, divisor); -} - -/* This function returns a new context for Barrett based operations on - * the modulus M. This context needs to be released using - * _gcry_mpi_barrett_free. If COPY is true M will be transferred to - * the context and the user may change M. If COPY is false, M may not - * be changed until gcry_mpi_barrett_free has been called. - */ -mpi_barrett_t mpi_barrett_init(MPI m, int copy) -{ - mpi_barrett_t ctx; - MPI tmp; - - mpi_normalize(m); - ctx = kcalloc(1, sizeof(*ctx), GFP_KERNEL); - if (!ctx) - return NULL; - - if (copy) { - ctx->m = mpi_copy(m); - ctx->m_copied = 1; - } else - ctx->m = m; - - ctx->k = mpi_get_nlimbs(m); - tmp = mpi_alloc(ctx->k + 1); - - /* Barrett precalculation: y = floor(b^(2k) / m). */ - mpi_set_ui(tmp, 1); - mpi_lshift_limbs(tmp, 2 * ctx->k); - mpi_fdiv_q(tmp, tmp, m); - - ctx->y = tmp; - ctx->r1 = mpi_alloc(2 * ctx->k + 1); - ctx->r2 = mpi_alloc(2 * ctx->k + 1); - - return ctx; -} - -void mpi_barrett_free(mpi_barrett_t ctx) -{ - if (ctx) { - mpi_free(ctx->y); - mpi_free(ctx->r1); - mpi_free(ctx->r2); - if (ctx->r3) - mpi_free(ctx->r3); - if (ctx->m_copied) - mpi_free(ctx->m); - kfree(ctx); - } -} - - -/* R = X mod M - * - * Using Barrett reduction. Before using this function - * _gcry_mpi_barrett_init must have been called to do the - * precalculations. CTX is the context created by this precalculation - * and also conveys M. If the Barret reduction could no be done a - * straightforward reduction method is used. - * - * We assume that these conditions are met: - * Input: x =(x_2k-1 ...x_0)_b - * m =(m_k-1 ....m_0)_b with m_k-1 != 0 - * Output: r = x mod m - */ -void mpi_mod_barrett(MPI r, MPI x, mpi_barrett_t ctx) -{ - MPI m = ctx->m; - int k = ctx->k; - MPI y = ctx->y; - MPI r1 = ctx->r1; - MPI r2 = ctx->r2; - int sign; - - mpi_normalize(x); - if (mpi_get_nlimbs(x) > 2*k) { - mpi_mod(r, x, m); - return; - } - - sign = x->sign; - x->sign = 0; - - /* 1. q1 = floor( x / b^k-1) - * q2 = q1 * y - * q3 = floor( q2 / b^k+1 ) - * Actually, we don't need qx, we can work direct on r2 - */ - mpi_set(r2, x); - mpi_rshift_limbs(r2, k-1); - mpi_mul(r2, r2, y); - mpi_rshift_limbs(r2, k+1); - - /* 2. r1 = x mod b^k+1 - * r2 = q3 * m mod b^k+1 - * r = r1 - r2 - * 3. if r < 0 then r = r + b^k+1 - */ - mpi_set(r1, x); - if (r1->nlimbs > k+1) /* Quick modulo operation. */ - r1->nlimbs = k+1; - mpi_mul(r2, r2, m); - if (r2->nlimbs > k+1) /* Quick modulo operation. */ - r2->nlimbs = k+1; - mpi_sub(r, r1, r2); - - if (mpi_has_sign(r)) { - if (!ctx->r3) { - ctx->r3 = mpi_alloc(k + 2); - mpi_set_ui(ctx->r3, 1); - mpi_lshift_limbs(ctx->r3, k + 1); - } - mpi_add(r, r, ctx->r3); - } - - /* 4. while r >= m do r = r - m */ - while (mpi_cmp(r, m) >= 0) - mpi_sub(r, r, m); - - x->sign = sign; -} - - -void mpi_mul_barrett(MPI w, MPI u, MPI v, mpi_barrett_t ctx) -{ - mpi_mul(w, u, v); - mpi_mod_barrett(w, w, ctx); -} |