import hashlib, hmac
seed = bytes.fromhex("33139046aad30472f99f3e7682837035fba0dfe3877d9da417c602a278d97cf9")
assert hashlib.sha256(seed).hexdigest() == "2d4af475024527d020dd068ac9a757ab8a72a55f1b8569b5dfe3ee79ca698eca"
ref = "DRW-001665"
# Eligible ticket numbers frozen after sales closed and payments were reconciled
ranges = [(1, 7)]
setHash = hashlib.sha256("\n".join(f"{a}-{b}" for a, b in ranges).encode()).hexdigest()
assert setHash == "3791968fee79a54bfcf3e65ea4a6aeef457df5c254e7b9ba433e1980dec6e6e2"
m = sum(b - a + 1 for a, b in ranges)
randomness = "a35bd8f04a9e7e2c7bfeabfa209ea3519870593f5093230683b5637c4a7d2a8c"  # the RNG service output above
limit = ((1 << 48) // m) * m
used = set()
for rank in range(1, 1 + 1):   # selection 1, then alternates / further prizes
    c = 0
    while True:
        part = f"{rank}|" if rank > 1 else ""
        msg = f"GBC-RNG-v1|{ref}|{m}|{setHash}|{randomness}|{part}{c}".encode()
        v = int.from_bytes(hmac.new(seed, msg, hashlib.sha256).digest()[:6], "big")
        c += 1
        if v >= limit or (v % m + 1) in used:
            continue
        k = v % m + 1
        used.add(k)
        break
    for a, b in ranges:
        if k <= b - a + 1:
            print("selection", rank, "ticket", a + k - 1)
            break
        k -= b - a + 1
# (a prize raffle with "one prize per person" also skips a buyer's other tickets — the server applies that rule from the frozen data)