mbedtls_ecp_gen_privkey_sw: generalize to mbedtls_mpi_random
Rename mbedtls_ecp_gen_privkey_sw to mbedtls_mpi_random since it has no particular connection to elliptic curves beyond the fact that its operation is defined by the deterministic ECDSA specification. This is a generic function that generates a random MPI between 1 inclusive and N exclusive. Slightly generalize the function to accept a different lower bound, which adds a negligible amount of complexity. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
parent
7888073147
commit
8cfffb30b3
4 changed files with 119 additions and 99 deletions
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@ -3093,15 +3093,17 @@ cleanup:
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#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
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MBEDTLS_STATIC_TESTABLE
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int mbedtls_ecp_gen_privkey_sw( const mbedtls_mpi *N, size_t n_bits,
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mbedtls_mpi *d,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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int mbedtls_mpi_random( mbedtls_mpi *X,
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mbedtls_mpi_sint min,
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const mbedtls_mpi *N,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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/* SEC1 3.2.1: Generate d such that 1 <= n < N */
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int ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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/* SEC1 3.2.1: Generate X such that 1 <= n < N */
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int ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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int count = 0;
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unsigned cmp = 0;
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size_t n_bits = mbedtls_mpi_bitlen( N );
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size_t n_bytes = ( n_bits + 7 ) / 8;
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/*
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@ -3114,8 +3116,8 @@ int mbedtls_ecp_gen_privkey_sw( const mbedtls_mpi *N, size_t n_bits,
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*/
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do
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{
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MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( d, n_bytes, f_rng, p_rng ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( d, 8 * n_bytes - n_bits ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( X, n_bytes, f_rng, p_rng ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( X, 8 * n_bytes - n_bits ) );
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/*
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* Each try has at worst a probability 1/2 of failing (the msb has
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@ -3128,17 +3130,17 @@ int mbedtls_ecp_gen_privkey_sw( const mbedtls_mpi *N, size_t n_bits,
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*/
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if( ++count > 30 )
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{
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ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
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ret = MBEDTLS_ERR_MPI_NOT_ACCEPTABLE;
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goto cleanup;
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}
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ret = mbedtls_mpi_lt_mpi_ct( d, N, &cmp );
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ret = mbedtls_mpi_lt_mpi_ct( X, N, &cmp );
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if( ret != 0 )
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{
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goto cleanup;
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}
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}
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while( mbedtls_mpi_cmp_int( d, 1 ) < 0 || cmp != 1 );
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while( mbedtls_mpi_cmp_int( X, min ) < 0 || cmp != 1 );
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cleanup:
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return( ret );
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@ -3164,8 +3166,7 @@ int mbedtls_ecp_gen_privkey( const mbedtls_ecp_group *grp,
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#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
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if( mbedtls_ecp_get_type( grp ) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS )
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return( mbedtls_ecp_gen_privkey_sw( &grp->N, grp->nbits, d,
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f_rng, p_rng ) );
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return( mbedtls_mpi_random( d, 1, &grp->N, f_rng, p_rng ) );
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#endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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@ -77,25 +77,36 @@ int mbedtls_ecp_gen_privkey_mx( size_t n_bits,
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#endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
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#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
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/** Generate a private key on a short Weierstrass curve.
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/** Generate a random number uniformly in a range.
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*
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* This function generates a random number between \p min inclusive and
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* \p N exclusive.
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*
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* The procedure complies with RFC 6979 §3.3 (deterministic ECDSA)
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* when the RNG is a suitably parametrized instance of HMAC_DRBG.
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* when the RNG is a suitably parametrized instance of HMAC_DRBG
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* and \p min is \c 1.
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*
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* \p N The upper bound of the range.
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* \p n_bits The size of \p N in bits. This value must be correct,
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* otherwise the result is unpredictable.
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* \param d A random number, uniformly generated in the range [1, N-1].
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* \param f_rng The RNG function.
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* \param p_rng The RNG context to be passed to \p f_rng.
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* \note There are `N - min` possible outputs. The lower bound
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* \p min can be reached, but the upper bound \p N cannot.
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*
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* \return \c 0 on success.
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* \return \c MBEDTLS_ERR_ECP_xxx or MBEDTLS_ERR_MPI_xxx on failure.
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* \param X The destination MPI. This must point to an initialized MPI.
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* \param min The minimum value to return.
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* It must be nonnegative.
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* \param N The upper bound of the range, exclusive.
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* In other words, this is one plus the maximum value to return.
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* \p N must be strictly larger than \p min.
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* \param f_rng The RNG function to use. This must not be \c NULL.
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* \param p_rng The RNG parameter to be passed to \p f_rng.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if a memory allocation failed.
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* \return Another negative error code on failure.
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*/
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int mbedtls_ecp_gen_privkey_sw( const mbedtls_mpi *N, size_t n_bits,
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mbedtls_mpi *d,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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int mbedtls_mpi_random( mbedtls_mpi *X,
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mbedtls_mpi_sint min,
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const mbedtls_mpi *N,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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#endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
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#endif /* MBEDTLS_TEST_HOOKS && MBEDTLS_ECP_C */
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@ -312,95 +312,104 @@ genkey_mx_known_answer:447:"ffffffffffffffffffffffffffffffffffffffffffffffffffff
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ECP generate Montgomery key: Curve448, not enough entropy
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genkey_mx_known_answer:447:"4f0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f30313233343536":""
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ECP generate in range: 4
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genkey_sw_many:"04":1000
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MPI random in range: 1..4
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mpi_random_many:1:"04":1000
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ECP generate in range: 5
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genkey_sw_many:"05":1000
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MPI random in range: 1..5
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mpi_random_many:1:"05":1000
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ECP generate in range: 6
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genkey_sw_many:"06":1000
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MPI random in range: 1..6
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mpi_random_many:1:"06":1000
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ECP generate in range: 7
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genkey_sw_many:"07":1000
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MPI random in range: 1..7
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mpi_random_many:1:"07":1000
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ECP generate in range: 8
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genkey_sw_many:"08":1000
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MPI random in range: 1..8
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mpi_random_many:1:"08":1000
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ECP generate in range: 9
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genkey_sw_many:"09":1000
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MPI random in range: 1..9
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mpi_random_many:1:"09":1000
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ECP generate in range: 10
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genkey_sw_many:"0a":1000
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MPI random in range: 1..10
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mpi_random_many:1:"0a":1000
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ECP generate in range: 11
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genkey_sw_many:"0b":1000
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MPI random in range: 1..11
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mpi_random_many:1:"0b":1000
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ECP generate in range: 12
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genkey_sw_many:"0c":1000
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MPI random in range: 1..12
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mpi_random_many:1:"0c":1000
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ECP generate in range: 255
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genkey_sw_many:"ff":100
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MPI random in range: 1..255
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mpi_random_many:1:"ff":100
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ECP generate in range: 256
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genkey_sw_many:"0100":100
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MPI random in range: 1..256
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mpi_random_many:1:"0100":100
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ECP generate in range: 257
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genkey_sw_many:"0101":100
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MPI random in range: 1..257
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mpi_random_many:1:"0101":100
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ECP generate in range: 272
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genkey_sw_many:"0110":100
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MPI random in range: 1..272
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mpi_random_many:1:"0110":100
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ECP generate in range: 2^64-1
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genkey_sw_many:"ffffffffffffffff":100
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MPI random in range: 1..2^64-1
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mpi_random_many:1:"ffffffffffffffff":100
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ECP generate in range: 2^64
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genkey_sw_many:"010000000000000000":100
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MPI random in range: 1..2^64
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mpi_random_many:1:"010000000000000000":100
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ECP generate in range: 2^64+1
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genkey_sw_many:"010000000000000001":100
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MPI random in range: 1..2^64+1
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mpi_random_many:1:"010000000000000001":100
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ECP generate in range: 2^64+2^63
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genkey_sw_many:"018000000000000000":100
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MPI random in range: 1..2^64+2^63
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mpi_random_many:1:"018000000000000000":100
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ECP generate in range: 2^65-1
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genkey_sw_many:"01ffffffffffffffff":100
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MPI random in range: 1..2^65-1
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mpi_random_many:1:"01ffffffffffffffff":100
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ECP generate in range: 2^65
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genkey_sw_many:"020000000000000000":100
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MPI random in range: 1..2^65
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mpi_random_many:1:"020000000000000000":100
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ECP generate in range: 2^65+1
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genkey_sw_many:"020000000000000001":100
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MPI random in range: 1..2^65+1
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mpi_random_many:1:"020000000000000001":100
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ECP generate in range: 2^65+2^64
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genkey_sw_many:"030000000000000000":100
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MPI random in range: 1..2^65+2^64
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mpi_random_many:1:"030000000000000000":100
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ECP generate in range: 2^66+2^65
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genkey_sw_many:"060000000000000000":100
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MPI random in range: 1..2^66+2^65
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mpi_random_many:1:"060000000000000000":100
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ECP generate in range: 2^71-1
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genkey_sw_many:"7fffffffffffffffff":100
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MPI random in range: 1..2^71-1
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mpi_random_many:1:"7fffffffffffffffff":100
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ECP generate in range: 2^71
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genkey_sw_many:"800000000000000000":100
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MPI random in range: 1..2^71
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mpi_random_many:1:"800000000000000000":100
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ECP generate in range: 2^71+1
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genkey_sw_many:"800000000000000001":100
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MPI random in range: 1..2^71+1
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mpi_random_many:1:"800000000000000001":100
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ECP generate in range: 2^71+2^63
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genkey_sw_many:"c00000000000000000":100
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MPI random in range: 1..2^71+2^63
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mpi_random_many:1:"c00000000000000000":100
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ECP generate in range: 2^72-1
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genkey_sw_many:"ffffffffffffffffff":100
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MPI random in range: 1..2^72-1
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mpi_random_many:1:"ffffffffffffffffff":100
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ECP generate in range: 2^72
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genkey_sw_many:"01000000000000000000":100
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MPI random in range: 1..2^72
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mpi_random_many:1:"01000000000000000000":100
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ECP generate in range: 2^72+1
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genkey_sw_many:"01000000000000000001":100
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MPI random in range: 1..2^72+1
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mpi_random_many:1:"01000000000000000001":100
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ECP generate in range: 2^72+2^63
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genkey_sw_many:"01800000000000000000":100
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MPI random in range: 1..2^72+2^63
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mpi_random_many:1:"01800000000000000000":100
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MPI random in range: 0..4
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mpi_random_many:0:"04":1000
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MPI random in range: 2..4
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mpi_random_many:1:"04":1000
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MPI random in range: 3..4
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mpi_random_many:1:"04":1000
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ECP read key #1 (short weierstrass, too small)
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depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
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@ -1324,7 +1324,7 @@ exit:
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/* END_CASE */
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/* BEGIN_CASE depends_on:MBEDTLS_TEST_HOOKS:MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
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void genkey_sw_many( data_t *bound_bytes, int iterations )
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void mpi_random_many( int min, data_t *bound_bytes, int iterations )
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{
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/* Generate numbers in the range 1..bound-1. Do it iterations times.
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* This function assumes that the value of bound is at least 2 and
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@ -1332,11 +1332,11 @@ void genkey_sw_many( data_t *bound_bytes, int iterations )
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* effectively never occurs.
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*/
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mbedtls_mpi bound;
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mbedtls_mpi upper_bound;
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size_t n_bits;
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mbedtls_mpi result;
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size_t b;
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/* If bound is small, stats[b] is the number of times the value b
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/* If upper_bound is small, stats[b] is the number of times the value b
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* has been generated. Otherwise stats[b] is the number of times a
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* value with bit b set has been generated. */
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size_t *stats = NULL;
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@ -1344,12 +1344,12 @@ void genkey_sw_many( data_t *bound_bytes, int iterations )
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int full_stats;
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size_t i;
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mbedtls_mpi_init( &bound );
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mbedtls_mpi_init( &upper_bound );
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mbedtls_mpi_init( &result );
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TEST_EQUAL( 0, mbedtls_mpi_read_binary( &bound,
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TEST_EQUAL( 0, mbedtls_mpi_read_binary( &upper_bound,
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bound_bytes->x, bound_bytes->len ) );
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n_bits = mbedtls_mpi_bitlen( &bound );
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n_bits = mbedtls_mpi_bitlen( &upper_bound );
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/* Consider a bound "small" if it's less than 2^5. This value is chosen
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* to be small enough that the probability of missing one value is
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* negligible given the number of iterations. It must be less than
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@ -1370,12 +1370,11 @@ void genkey_sw_many( data_t *bound_bytes, int iterations )
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for( i = 0; i < (size_t) iterations; i++ )
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{
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mbedtls_test_set_step( i );
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TEST_EQUAL( 0, mbedtls_ecp_gen_privkey_sw(
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&bound, n_bits, &result,
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mbedtls_test_rnd_std_rand, NULL ) );
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TEST_EQUAL( 0, mbedtls_mpi_random( &result, min, &upper_bound,
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mbedtls_test_rnd_std_rand, NULL ) );
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TEST_ASSERT( mbedtls_mpi_cmp_mpi( &result, &bound ) < 0 );
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TEST_ASSERT( mbedtls_mpi_cmp_int( &result, 1 ) >= 0 );
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TEST_ASSERT( mbedtls_mpi_cmp_mpi( &result, &upper_bound ) < 0 );
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TEST_ASSERT( mbedtls_mpi_cmp_int( &result, min ) >= 0 );
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if( full_stats )
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{
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uint8_t value;
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@ -1425,7 +1424,7 @@ void genkey_sw_many( data_t *bound_bytes, int iterations )
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}
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exit:
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mbedtls_mpi_free( &bound );
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mbedtls_mpi_free( &upper_bound );
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mbedtls_mpi_free( &result );
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mbedtls_free( stats );
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}
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