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Provably fair mystery box and case opening sites

By Elena MorettiLead fairness auditor Fact-checked by Marcus Hale Updated

Case opening and mystery box sites draw one item at random from a published list. That makes them a natural fit for provably fair systems: the site commits to a secret seed before you open, reveals it afterwards, and you recompute the draw yourself. In practice, the quality of that proof varies a lot. Some sites publish the exact function that turns seeds into an item. Others only say the word "provably fair" and keep the method behind a login.

This guide sets out what nine of the most used sites publish about their fairness method, based on their own fairness and terms pages read in November 2026. It is not a ranking and gives no scores. We have not logged bet-level audits at any of these sites yet.

What a complete fairness scheme needs

For a case or box opening, look for five things:

  1. A committed server seed. You see its hash before you open, and the seed itself after.
  2. An input you control or nobody controls. Either a client seed you can edit, or external entropy such as a future blockchain block hash.
  3. A nonce. A counter that changes with each opening, so the same seeds give a new result each time.
  4. A published mapping. The exact code that turns the hash into a ticket or roll, and the ticket ranges for each item.
  5. Access to your history. Seeds, nonces and block references for past openings, so you can check any one of them.

Battles add a twist. Because other players are involved, a client seed from one player would give that player an edge. Most sites replace it with the hash of a future block from the EOS blockchain, which nobody can predict when the battle starts.

What each site publishes

Site Hash and inputs (as published) Battles Public code Notes
Packdraw SHA-512 of client seed : server seed : nonce, read as a big integer, mod 1,000,000, plus 1 = ticket Client seed replaced by a future EOS block hash; jackpot battles use SHA-256 of the block hash over the total ticket count Yes, functions shown on the fairness page Server seed hash shown in your profile before purchase; ticket ranges shown in pack details
CSGORoll Per-game server seed with SHA-256 commitment plus a pre-committed future EOS block hash; Roll game uses SHA-512 of seeds and nonce, first 5 hex characters, rejected above 10,000 EOS block hash as external entropy Yes, verifier links on the fairness page Games before #6788734 used a 10 million SHA-256 hash chain; dated notes for older RNG versions
Skinrave Server seed, client seed and nonce for cases; tickets 0 to 9,999 for battles Server seed plus future EOS block id, slot number and round number Yes, code on the fairness page Seed shown red while still hashed; change your client seed to reveal it. States 4 to 10% edge on cases
HypeDrop Not readable: the provably fair page sat behind a bot check when we tried Not read Not confirmed Its FAQ has entries on fairness and on viewing product odds
Skin.Club Says roll and seed-change history is public and other players' results can be inspected Not stated on the page we read Not shown on the public page Formula not given on the public page
Key-Drop Says every spin uses a provably fair algorithm Not stated No, the page redirects to a login screen Method not visible without an account
Hellcase Not stated in the terms of use Not stated Not found Fairness method may be in its FAQ, which we did not read
RillaBox Calls itself "100% provably fair" Not stated Not found The fairness page did not render for us
Courtyard Pack contents "determined randomly" per its terms Not applicable No No seed scheme published; buyback uses a fair market value Courtyard sets and does not disclose

Reading the table

Packdraw is the clearest of the physical-prize sites. Its fairness page gives the combine and ticket functions in a few lines of code, so you can rebuild any opening. Our guide on how to verify a case opening result walks through one.

CSGORoll changed its system for newer games to a per-game seed plus an EOS block, and keeps notes on older versions with nonce ranges and dates. That history is useful: a site that documents its changes lets you verify old results under the rules that applied then.

Skinrave publishes code for each game and its house edges, from about 0.5% on its blackjack-style game to 4 to 10% on cases and 6.66% on Bait. Knowing the edge matters as much as checking the seed.

Skin.Club, Key-Drop, HypeDrop, Hellcase and RillaBox may well run sound systems, but we could not read the formula on a public page. Until a method is published, "provably fair" is a claim you cannot test.

Courtyard is a different model. Its packs are not seed-based, and its buyback offer is set by a model it does not disclose.

Fair draw, unfair price

A verifiable draw tells you the site picked from the published odds. It does not tell you the odds are good. To judge a box, multiply each item's value by its probability and add them. If a $25 box has an expected value of $21.18, the box keeps about 15% on average, however fair the draw.

Check the exit route too. Packdraw credits exchanged items at the value shown at the time of exchange. HypeDrop charges an exchange fee shown when you exchange. Hellcase says its balance cannot be withdrawn at all. These terms change your real return more than any seed scheme.

Red flags

  • A fairness page that requires login, or that describes the idea without the code.
  • No way to see the server seed hash before you open.
  • Battles that use a player's client seed instead of external entropy.
  • Ticket ranges or item odds that are not shown on the box page.
  • Item values that can change between winning and exchanging, without the rule being stated. Packdraw states this rule in its terms; check that the site you use does too.

Sources

Key terms

Provably fair
A cryptographic method that lets you confirm a game result was set before your bet and left untouched afterwards.
Server seed
The casino's secret random value that, together with your client seed and the nonce, decides each bet result.
Hashed server seed
The SHA-256 digest of the casino's secret server seed, published before any bet as proof the seed is locked in.
Client seed
The player's own input to every provably fair result, set or edited by you so the casino cannot work out outcomes in advance.
Nonce
A bet counter that goes up by one for each wager on the same seed pair, so no two bets share a result.
SHA-256
A cryptographic hash that maps any input to a fixed 256-bit digest; casinos use it to commit to server seeds.
House edge
The average percentage of every wager that a game is built to keep for the casino.
Mystery box
A box sold at a fixed price that reveals one item at random from a published list of items and odds.
Case battle
A mode where several players open the same cases or boxes and the highest total value usually takes all the items.

Frequently asked questions

Which case opening sites publish their fairness code?
Of the nine we checked, Packdraw, CSGORoll and Skinrave publish the formula or verifier code on public pages.
Why do battles use an EOS block hash?
A player-set client seed would give that player an edge, so sites use the hash of a future EOS block that nobody can predict when the battle starts.
Does provably fair mean the box is good value?
No. It proves the draw matched the published odds. The expected value from those odds decides the price you pay on average.
Is Key-Drop provably fair?
Key-Drop says every spin uses a provably fair algorithm, but its fairness page redirected to a login screen when we checked, so the method was not publicly visible.
Has Provably Legit audited these sites?
Not yet. This page records what each site publishes; bet-level audits will be added once logged.