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| from ecdsa.curves import Curve | |
| from ecdsa.ellipticcurve import CurveFp, Point | |
| from .signature import ( | |
| ALPHA, | |
| BETA, | |
| CONSTANT_POINTS, | |
| EC_ORDER, | |
| FIELD_PRIME, | |
| N_ELEMENT_BITS_HASH, | |
| SHIFT_POINT, | |
| ) | |
| from ...python.utils import from_bytes, to_bytes | |
| curve_stark = CurveFp(FIELD_PRIME, ALPHA, BETA) | |
| LOW_PART_BITS = 248 | |
| LOW_PART_MASK = 2**248 - 1 | |
| HASH_SHIFT_POINT = Point(curve_stark, SHIFT_POINT[0], SHIFT_POINT[1], EC_ORDER) | |
| P_0 = Point(curve_stark, CONSTANT_POINTS[2][0], CONSTANT_POINTS[2][1], EC_ORDER) | |
| P_1 = Point(curve_stark, CONSTANT_POINTS[2 + LOW_PART_BITS][0], CONSTANT_POINTS[2 + LOW_PART_BITS][1], EC_ORDER) | |
| P_2 = Point(curve_stark, CONSTANT_POINTS[2 + N_ELEMENT_BITS_HASH][0], CONSTANT_POINTS[2 + N_ELEMENT_BITS_HASH][1], EC_ORDER) | |
| P_3 = Point(curve_stark, CONSTANT_POINTS[2 + N_ELEMENT_BITS_HASH + LOW_PART_BITS][0], CONSTANT_POINTS[2 + N_ELEMENT_BITS_HASH + LOW_PART_BITS][1], EC_ORDER) | |
| def process_single_element(element: int, p1, p2) -> Point: | |
| assert 0 <= element < FIELD_PRIME, "Element integer value is out of range" | |
| high_nibble = element >> LOW_PART_BITS | |
| low_part = element & LOW_PART_MASK | |
| return low_part * p1 + high_nibble * p2 | |
| def pedersen_hash(x: int, y: int) -> int: | |
| """ | |
| Computes the Starkware version of the Pedersen hash of x and y. | |
| The hash is defined by: | |
| shift_point + x_low * P_0 + x_high * P1 + y_low * P2 + y_high * P3 | |
| where x_low is the 248 low bits of x, x_high is the 4 high bits of x and similarly for y. | |
| shift_point, P_0, P_1, P_2, P_3 are constant points generated from the digits of pi. | |
| """ | |
| return ( | |
| HASH_SHIFT_POINT + process_single_element(x, P_0, P_1) + process_single_element(y, P_2, P_3) | |
| ).x() | |
| def pedersen_hash_func(x: bytes, y: bytes) -> bytes: | |
| """ | |
| A variant of 'pedersen_hash', where the elements and their resulting hash are in bytes. | |
| """ | |
| assert len(x) == len(y) == 32, "Unexpected element length." | |
| return to_bytes(pedersen_hash(*(from_bytes(element) for element in (x, y)))) |
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