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🏆🏆 Aleo ZK Hackathon 2023 - Winner for Multiple Bounties 🏆🏆

We allow users to generate Leo code that splits a given secret into $n$ shares, of which $k$ is sufficient to recover the original secret when all put back together.

  • $k$ is the number of evaluations required to reconstruct the secret. Maximum value it can take is 32 (bounded by Leo's array size).
  • $n$ is the number of evaluations you want. Again, $k$ of them will suffice for recovery.

Considerations

  1. Leo does not support variable-sized arrays. To achieve fine-grained functionality, we present TypeScript code that generates SSS as Leo code for given $(k, n)$ parameters.
  2. We support secret splitting up to 32 pieces $(k \leq 32)$, but you can get as many evaluations (of your secret polynomial) as you want, up to 1024 points. Out of these, $k$ of them will suffice for recovery.

How to Use

Make sure you have an .env file ready for Aleo. It should look like the following:

NETWORK=testnet3 # or another network of your choice
PRIVATE_KEY=your-private-key # you can generate one with `leo account new`

You must first generate the contract for $(k, n)$ parameters of your choice. Then, you can either use leo run or our wrappers within package.json to split a share, or recover a secret from evaluations. We describe each step within this section. We are using Bun runtime, which can be installed via:

curl -fsSL https://bun.sh/install | bash

Generating the Aleo contract

# bun gen <n> <k>
bun gen 10 3

This will output a outputs/main.leo that contains all required Leo code to split a given secret and to recover it back, following given parameters. This will also prepare a inputs/shamir.in file in which user will put the inputs for the recover function (more on this later).

Splitting the secret

After the codegen phase, run the following command from the root directory to split the secret.

Warning

Your secret needs to be a field element.

# bun split <secret>
bun split 96024field

# or with leo
leo run split 96024field

See example output for n=10 
[
  [
    [
      1field,
      5706202619594540077989992285094960082181821933679081517586770005249329693829field
    ],
    [
      2field,
      2967943489760709731731159631408373632987744532204099207238306554581250148197field
    ],
    [
      3field,
      229684359926879385472326977721787183793667130729116896889843103913170602565field
    ],
    [
      4field,
      5935886979521419463462319262816747265975489064408198414476613109162500295974field
    ],
    [
      5field,
      3197627849687589117203486609130160816781411662933216104128149658494420750342field
    ],
    [
      6field,
      459368719853758770944653955443574367587334261458233793779686207826341204710field
    ],
    [
      7field,
      6165571339448298848934646240538534449769156195137315311366456213075670898119field
    ],
    [
      8field,
      3427312209614468502675813586851948000575078793662333001017992762407591352487field
    ],
    [
      9field,
      689053079780638156416980933165361551381001392187350690669529311739511806855field
    ],
    [
      10field,
      6395255699375178234406973218260321633562823325866432208256299316988841500264field
    ]
  ]
]

Recovering the secret

Grab $k$ of the field elements outputted in step-2, and place them into /inputs/shamir.in file. For $k=3$, the file should already look as follows:

[recover]
evals: [[field; 2]; 3] = [
  /* your inputs shall be pasted here */
];

You basically need to place any $k=3$ elements outputted by step-2 here. A valid input would look as follows:

[recover]
evals: [[field; 2]; 3] = [
  [
    6field,
    8085709056458833402027478012051955642975336737559694498490266579832655590565field
  ],
  [
    7field,
    4218449185145615173800512391527665203751554882089979277338887121280432824514field
  ],
  [
    8field,
    2480279192904644138280696900233670979007061890715911133616962794733481061345field
  ]
];

After placing this input, you can call the recover algorithm as follows:

bun recover

# or with leo
leo run recover

And you have the secret back.

Testing

We have written small tests that runs several cases of $(k, n)$ where a random secret is splitted and then recovered again. To run them:

bun run test

Note that this is not bun test, but instead calls the test script within package.json which has some parameters passed into Bun.