PLA+ Marble – spring batch

Published record

Algorithm

fld-draw-v1

Commitment (SHA-256 of the seed, published before entries opened)

0527ccd176897fcefc55f371ac82f8e0129de86079c96a4219b25488d7b98186

Seed (revealed after the draw)

21cd2aa5a75451ed74c28cc56a8c204c487e6c8a8eae10549d2758b53e07b28e

Entry list fingerprint (SHA-256 of the sorted numbers joined by commas)

66f396c11f7d352910573cbc62ff9d62516c36d9103520f74c56e287f6d5dc27

How the draw works

1. Before entries opened we generated a secret 32-byte seed and published its SHA-256 fingerprint (the commitment). Nobody can change the seed afterwards without the fingerprint changing.
2. When entries closed, the list of entry numbers was frozen and sorted ascending.
3. A random stream is produced with HMAC-SHA256: key = the seed bytes, message = "fld-draw-v1:" followed by a counter 0, 1, 2, … Each 32-byte block gives eight unsigned 32-bit big-endian numbers.
4. Numbers in a range 0…n−1 are taken by rejection sampling (values at or above the largest multiple of n below 2³² are skipped), so there is no bias.
5. The entry list is shuffled with Fisher–Yates from the last position down to the second: for each position i a random j between 0 and i is drawn and the two entries are swapped.
6. Winners are taken in the resulting order until the allocation is used up; each entry receives at most the quantity it asked for.

Draw order

1. #0024 drawn – did not buy in time
2. #0021 drawn – bought
3. #0018 drawn – did not buy in time
4. #0012 drawn – bought
5. #0002 drawn – bought
6. #0014 drawn – bought
7. #0025 drawn – bought
8. #0023 drawn – bought
9. #0001 drawn – bought
10. #0005 drawn – bought
11. #0019 drawn – bought
12. #0026 drawn – bought
13. #0011 drawn – bought
14. #0004 drawn – bought
15. #0017 drawn – did not buy in time
16. #0015 drawn – bought
17. #0006 drawn – bought
18. #0020 drawn – bought
19. #0008 drawn – bought
20. #0009 drawn – bought
21. #0003 drawn – bought
22. #0022 drawn – bought
23. #0010 drawn – bought
24. #0016 drawn – bought
25. #0007 drawn – bought
26. #0013 drawn – bought