mw22_dvarhash.py

from functools import reduce

def fnv(data: bytes, prime: int, basis: int, mod: int):
    return reduce(lambda hash, b: ((hash * prime) ^ b) % mod, data, basis)

def fnv_a(data: bytes, prime: int, basis: int, mod: int):
    return reduce(lambda hash, b: ((hash ^ b) * prime) % mod, data, basis)

def find_basis_a(hash: int, data: bytes, prime: int, mod: int):
    # reverse the operations using the prime's modular multiplicative inverse
    inverse = pow(prime, -1, mod)
    return fnv(reversed(data), prime=inverse, basis=hash, mod=mod)

def dvar_hash(name: str):
    return fnv_a(name.lower().encode(),
                 prime=0x10000000233,
                 basis=0x7238A5E2001AEB8E,
                 mod=2**64)

def main():
    names  = ["db_keyServer1",    "db_keyServer2",    "db_keyServer3"]
    hashes = [0xFB94649B6B0A4A16, 0xFB94639B6B0A47E3, 0xFB94629B6B0A45B0]

    prime = hashes[1] - hashes[2]
    print(f"prime {prime:X}")
    basis = find_basis_a(hashes[0], names[0].lower().encode(), prime, 2**64)
    print(f"basis {basis:X}")

    for name, expected in zip(names, hashes):
        print(f"hash {dvar_hash(name):016X} expected {expected:016X}")

if __name__ == "__main__":
    main()