INNER CODE UNIT · Python

hash_to_scalar

schollz/pake · ed25519_points.py:15

def hash_to_scalar(seed: str) -> bytes:
    """
    Generate a 32-byte scalar from a seed string using SHA-256.
    This mimics the hash-based point generation approach.
    """
    # Hash the seed multiple times to get sufficient entropy
    hash_input = seed.encode("utf-8")
    for _ in range(1000):  # Multiple rounds for better distribution
        hash_input = hashlib.sha256(hash_input).digest()

    # Take the first 32 bytes and clamp for ed25519
    scalar = bytearray(hash_input[:32])

    # Apply ed25519 scalar clamping
    scalar[0] &= 248  # Clear bottom 3 bits
    scalar[31] &= 127  # Clear top bit
    scalar[31] |= 64  # Set second-highest bit

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