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Fix ecp_gen_keypair()
Too few tries caused failures for some curves (esp. secp224k1)
This commit is contained in:
committed by
Paul Bakker
parent
2cb1a0c400
commit
6e8e34d61e
@ -1796,7 +1796,16 @@ int ecp_gen_keypair( ecp_group *grp, mpi *d, ecp_point *Q,
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MPI_CHK( mpi_read_binary( d, rnd, n_size ) );
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MPI_CHK( mpi_shift_r( d, 8 * n_size - grp->nbits ) );
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if( count++ > 10 )
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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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* a probability 1/2 of being 0, and then the result will be < N),
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* so after 30 tries failure probability is a most 2**(-30).
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*
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* For most curves, 1 try is enough with overwhelming probability,
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* since N starts with a lot of 1s in binary, but some curves
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* such as secp224k1 are actually very close to the worst case.
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*/
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if( ++count > 30 )
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return( POLARSSL_ERR_ECP_RANDOM_FAILED );
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}
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while( mpi_cmp_int( d, 1 ) < 0 ||
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