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RSA: remove unneeded temporaries

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Signed-off-by: Janos Follath <janos.follath@arm.com>
This commit is contained in:
Janos Follath 2023-12-27 10:33:00 +00:00 committed by Dave Rodgman
parent e6750b2a0b
commit 47ee770812
1 changed files with 3 additions and 18 deletions
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21
library/rsa.c
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@ -1056,18 +1056,9 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
/* Temporaries holding the blinded exponents for
* the mod p resp. mod q computation (if used). */
mbedtls_mpi DP_blind, DQ_blind;
/* Pointers to actual exponents to be used - either the unblinded
* or the blinded ones, depending on the presence of a PRNG. */
mbedtls_mpi *DP = &ctx->DP;
mbedtls_mpi *DQ = &ctx->DQ;
#else
/* Temporary holding the blinded exponent (if used). */
mbedtls_mpi D_blind;
/* Pointer to actual exponent to be used - either the unblinded
* or the blinded one, depending on the presence of a PRNG. */
mbedtls_mpi *D = &ctx->D;
#endif /* MBEDTLS_RSA_NO_CRT */
/* Temporaries holding the initial input and the double
@ -1143,8 +1134,6 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&D_blind, &P1, &Q1));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&D_blind, &D_blind, &R));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&D_blind, &D_blind, &ctx->D));
D = &D_blind;
#else
/*
* DP_blind = ( P - 1 ) * R + DP
@ -1155,8 +1144,6 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&DP_blind, &DP_blind,
&ctx->DP));
DP = &DP_blind;
/*
* DQ_blind = ( Q - 1 ) * R + DQ
*/
@ -1165,12 +1152,10 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&DQ_blind, &Q1, &R));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&DQ_blind, &DQ_blind,
&ctx->DQ));
DQ = &DQ_blind;
#endif /* MBEDTLS_RSA_NO_CRT */
#if defined(MBEDTLS_RSA_NO_CRT)
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, D, &ctx->N, &ctx->RN));
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, &D_blind, &ctx->N, &ctx->RN));
#else
/*
* Faster decryption using the CRT
@ -1179,8 +1164,8 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
* TQ = input ^ dQ mod Q
*/
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TP, &T, DP, &ctx->P, &ctx->RP));
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TQ, &T, DQ, &ctx->Q, &ctx->RQ));
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TP, &T, &DP_blind, &ctx->P, &ctx->RP));
MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TQ, &T, &DQ_blind, &ctx->Q, &ctx->RQ));
/*
* T = (TP - TQ) * (Q^-1 mod P) mod P