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145 lines
5.7 KiB
C
145 lines
5.7 KiB
C
/********************************************************************************************
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* SIDH: an efficient supersingular isogeny cryptography library
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*
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* Abstract: internal header file for P434
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*********************************************************************************************/
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#ifndef UTILS_H_
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#define UTILS_H_
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#include <openssl/base.h>
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#include "../crypto/internal.h"
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#include "sike.h"
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// Conversion macro from number of bits to number of bytes
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#define BITS_TO_BYTES(nbits) (((nbits)+7)/8)
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// Bit size of the field
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#define BITS_FIELD 434
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// Byte size of the field
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#define FIELD_BYTESZ BITS_TO_BYTES(BITS_FIELD)
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// Number of 64-bit words of a 224-bit element
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#define NBITS_ORDER 224
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#define NWORDS64_ORDER ((NBITS_ORDER+63)/64)
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// Number of elements in Alice's strategy
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#define A_max 108
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// Number of elements in Bob's strategy
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#define B_max 137
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// Word size size
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#define RADIX sizeof(crypto_word_t)*8
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// Byte size of a limb
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#define LSZ sizeof(crypto_word_t)
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#if defined(OPENSSL_64_BIT)
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// Number of words of a 434-bit field element
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#define NWORDS_FIELD 7
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// Number of "0" digits in the least significant part of p434 + 1
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#define ZERO_WORDS 3
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// U64_TO_WORDS expands |x| for a |crypto_word_t| array literal.
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#define U64_TO_WORDS(x) UINT64_C(x)
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#else
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// Number of words of a 434-bit field element
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#define NWORDS_FIELD 14
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// Number of "0" digits in the least significant part of p434 + 1
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#define ZERO_WORDS 6
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// U64_TO_WORDS expands |x| for a |crypto_word_t| array literal.
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#define U64_TO_WORDS(x) \
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(uint32_t)(UINT64_C(x) & 0xffffffff), (uint32_t)(UINT64_C(x) >> 32)
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#endif
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// Extended datatype support
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#if !defined(BORINGSSL_HAS_UINT128)
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typedef uint64_t uint128_t[2];
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#endif
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// The following functions return 1 (TRUE) if condition is true, 0 (FALSE) otherwise
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// Digit multiplication
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#define MUL(multiplier, multiplicand, hi, lo) digit_x_digit((multiplier), (multiplicand), &(lo));
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// If mask |x|==0xff.ff set |x| to 1, otherwise 0
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#define M2B(x) ((x)>>(RADIX-1))
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// Digit addition with carry
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#define ADDC(carryIn, addend1, addend2, carryOut, sumOut) \
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do { \
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crypto_word_t tempReg = (addend1) + (crypto_word_t)(carryIn); \
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(sumOut) = (addend2) + tempReg; \
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(carryOut) = M2B(constant_time_lt_w(tempReg, (crypto_word_t)(carryIn)) | \
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constant_time_lt_w((sumOut), tempReg)); \
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} while(0)
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// Digit subtraction with borrow
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#define SUBC(borrowIn, minuend, subtrahend, borrowOut, differenceOut) \
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do { \
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crypto_word_t tempReg = (minuend) - (subtrahend); \
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crypto_word_t borrowReg = M2B(constant_time_lt_w((minuend), (subtrahend))); \
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borrowReg |= ((borrowIn) & constant_time_is_zero_w(tempReg)); \
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(differenceOut) = tempReg - (crypto_word_t)(borrowIn); \
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(borrowOut) = borrowReg; \
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} while(0)
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/* Old GCC 4.9 (jessie) doesn't implement {0} initialization properly,
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which violates C11 as described in 6.7.9, 21 (similarily C99, 6.7.8).
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Defines below are used to work around the bug, and provide a way
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to initialize f2elem_t and point_proj_t structs.
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Bug has been fixed in GCC6 (debian stretch).
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*/
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#define F2ELM_INIT {{ {0}, {0} }}
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#define POINT_PROJ_INIT {{ F2ELM_INIT, F2ELM_INIT }}
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// Datatype for representing 434-bit field elements (448-bit max.)
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// Elements over GF(p434) are encoded in 63 octets in little endian format
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// (i.e., the least significant octet is located in the lowest memory address).
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typedef crypto_word_t felm_t[NWORDS_FIELD];
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// An element in F_{p^2}, is composed of two coefficients from F_p, * i.e.
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// Fp2 element = c0 + c1*i in F_{p^2}
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// Datatype for representing double-precision 2x434-bit field elements (448-bit max.)
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// Elements (a+b*i) over GF(p434^2), where a and b are defined over GF(p434), are
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// encoded as {a, b}, with a in the lowest memory portion.
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typedef struct {
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felm_t c0;
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felm_t c1;
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} fp2;
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// Our F_{p^2} element type is a pointer to the struct.
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typedef fp2 f2elm_t[1];
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// Datatype for representing double-precision 2x434-bit
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// field elements in contiguous memory.
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typedef crypto_word_t dfelm_t[2*NWORDS_FIELD];
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// Constants used during SIKE computation.
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struct params_t {
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// Stores a prime
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const crypto_word_t prime[NWORDS_FIELD];
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// Stores prime + 1
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const crypto_word_t prime_p1[NWORDS_FIELD];
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// Stores prime * 2
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const crypto_word_t prime_x2[NWORDS_FIELD];
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// Alice's generator values {XPA0 + XPA1*i, XQA0 + XQA1*i, XRA0 + XRA1*i}
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// in GF(prime^2), expressed in Montgomery representation
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const crypto_word_t A_gen[6*NWORDS_FIELD];
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// Bob's generator values {XPB0 + XPB1*i, XQB0 + XQB1*i, XRB0 + XRB1*i}
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// in GF(prime^2), expressed in Montgomery representation
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const crypto_word_t B_gen[6*NWORDS_FIELD];
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// Montgomery constant mont_R2 = (2^448)^2 mod prime
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const crypto_word_t mont_R2[NWORDS_FIELD];
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// Value 'one' in Montgomery representation
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const crypto_word_t mont_one[NWORDS_FIELD];
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// Value '6' in Montgomery representation
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const crypto_word_t mont_six[NWORDS_FIELD];
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// Fixed parameters for isogeny tree computation
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const unsigned int A_strat[A_max-1];
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const unsigned int B_strat[B_max-1];
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};
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// Point representation in projective XZ Montgomery coordinates.
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typedef struct {
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f2elm_t X;
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f2elm_t Z;
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} point_proj;
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typedef point_proj point_proj_t[1];
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#endif // UTILS_H_
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