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62733a8389
This reverts commit a7bdefb394.
I had accidentally mashed it together with another commit. I did
actually want to push both of them, but I'd rather push them
separately! So I'm backing out the combined blob, and I'll re-push
them with their proper comments and explanations.
77 lines
3.1 KiB
C
77 lines
3.1 KiB
C
/*
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* sshkeygen.h: routines used internally to key generation.
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*/
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/* ----------------------------------------------------------------------
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* A table of all the primes that fit in a 16-bit integer. Call
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* init_primes_array to make sure it's been initialised.
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*/
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#define NSMALLPRIMES 6542 /* number of primes < 65536 */
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extern const unsigned short *const smallprimes;
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void init_smallprimes(void);
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/* ----------------------------------------------------------------------
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* A system for making up random candidate integers during prime
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* generation. This unconditionally ensures that the numbers have the
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* right number of bits and are not divisible by any prime in the
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* smallprimes[] array above. It can also impose further constraints,
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* as documented below.
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*/
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typedef struct PrimeCandidateSource PrimeCandidateSource;
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/*
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* pcs_new: you say how many bits you want the prime to have (with the
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* usual semantics that an n-bit number is in the range [2^{n-1},2^n))
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* and also optionally specify what you want its topmost 'nfirst' bits
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* to be.
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*
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* (The 'first' system is used for RSA keys, where you need to arrange
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* that the product of your two primes is in a more tightly
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* constrained range than the factor of 4 you'd get by just generating
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* two (n/2)-bit primes and multiplying them.)
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*/
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PrimeCandidateSource *pcs_new(unsigned bits);
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PrimeCandidateSource *pcs_new_with_firstbits(unsigned bits,
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unsigned first, unsigned nfirst);
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/* Insist that generated numbers must be congruent to 'res' mod 'mod' */
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void pcs_require_residue(PrimeCandidateSource *s, mp_int *mod, mp_int *res);
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/* Convenience wrapper for the common case where res = 1 */
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void pcs_require_residue_1(PrimeCandidateSource *s, mp_int *mod);
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/* Insist that generated numbers must _not_ be congruent to 'res' mod
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* 'mod'. This is used to avoid being 1 mod the RSA public exponent,
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* which is small, so it only needs ordinary integer parameters. */
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void pcs_avoid_residue_small(PrimeCandidateSource *s,
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unsigned mod, unsigned res);
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/* Prepare a PrimeCandidateSource to actually generate numbers. This
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* function does last-minute computation that has to be delayed until
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* all constraints have been input. */
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void pcs_ready(PrimeCandidateSource *s);
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/* Actually generate a candidate integer. You must free the result, of
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* course. */
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mp_int *pcs_generate(PrimeCandidateSource *s);
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/* Free a PrimeCandidateSource. */
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void pcs_free(PrimeCandidateSource *s);
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/* Return some internal fields of the PCS. Used by testcrypt for
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* unit-testing this system. */
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void pcs_inspect(PrimeCandidateSource *pcs, mp_int **limit_out,
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mp_int **factor_out, mp_int **addend_out);
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/* Query functions for primegen to use */
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unsigned pcs_get_bits(PrimeCandidateSource *pcs);
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/* ----------------------------------------------------------------------
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* The top-level API for generating primes.
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*/
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/* This function consumes and frees the PrimeCandidateSource you give it */
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mp_int *primegen(PrimeCandidateSource *pcs,
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int phase, progfn_t pfn, void *pfnparam);
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