Differential D5352 Diff 16578 src/secp256k1/src/ecmult_impl.h

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src/secp256k1/src/ecmult_impl.h

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	/** Convert a number to WNAF notation. The number becomes represented by sum(2^i * wnaf[i], i=0..bits),			/** Convert a number to WNAF notation. The number becomes represented by sum(2^i * wnaf[i], i=0..bits),
	* with the following guarantees:			* with the following guarantees:
	* - each wnaf[i] is either 0, or an odd integer between -(1<<(w-1) - 1) and (1<<(w-1) - 1)			* - each wnaf[i] is either 0, or an odd integer between -(1<<(w-1) - 1) and (1<<(w-1) - 1)
	* - two non-zero entries in wnaf are separated by at least w-1 zeroes.			* - two non-zero entries in wnaf are separated by at least w-1 zeroes.
	* - the number of set values in wnaf is returned. This number is at most 256, and at most one more			* - the number of set values in wnaf is returned. This number is at most 256, and at most one more
	* than the number of bits in the (absolute value) of the input.			* than the number of bits in the (absolute value) of the input.
	*/			*/
	static int secp256k1_ecmult_wnaf(int wnaf, int len, const secp256k1_scalar a, int w) {			static int secp256k1_ecmult_wnaf(int wnaf, int len, const secp256k1_scalar a, int w) {
	secp256k1_scalar s = *a;			secp256k1_scalar s;
	int last_set_bit = -1;			int last_set_bit = -1;
	int bit = 0;			int bit = 0;
	int sign = 1;			int sign = 1;
	int carry = 0;			int carry = 0;

	VERIFY_CHECK(wnaf != NULL);			VERIFY_CHECK(wnaf != NULL);
	VERIFY_CHECK(0 <= len && len <= 256);			VERIFY_CHECK(0 <= len && len <= 256);
	VERIFY_CHECK(a != NULL);			VERIFY_CHECK(a != NULL);
	VERIFY_CHECK(2 <= w && w <= 31);			VERIFY_CHECK(2 <= w && w <= 31);

	memset(wnaf, 0, len * sizeof(wnaf[0]));			memset(wnaf, 0, len * sizeof(wnaf[0]));

				s = *a;
	if (secp256k1_scalar_get_bits(&s, 255, 1)) {			if (secp256k1_scalar_get_bits(&s, 255, 1)) {
	secp256k1_scalar_negate(&s, &s);			secp256k1_scalar_negate(&s, &s);
	sign = -1;			sign = -1;
	}			}

	while (bit < len) {			while (bit < len) {
	int now;			int now;
	int word;			int word;
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