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Dark Crystal Secrets

Dark Crystal's encryption wrapper around Shamir's Secret Shares implementation secrets.js-grempe.

Using a semantic versioning system, this module also provides backward compatibility to Dark Crystal records out there in the wild. This is required as we incrementally update Dark Crystal's encryption schemes, exploring, experimenting and improving our implementation.

dark-crystal-secrets

Example

const { pack, unpack. share, verify, combine } = require('dark-crystal-secretes')

const labelledSecret = pack('burried under my tree fort', 'treasure chest 1')
const shares = share(labelledSecret, 5, 3) // split into 5 parts, quorum 3

shares.forEach(share => console.log(validateShard(share, '2.0.0'))

const validity = verify(share.slice(0,3), '2.0.0')
console.log(validity)

const recoveredLabelledSecret = combine(share.slice(0,3), '2.0.0')
const { secret, label } = unpack(recoveredLabelledSecret, '2.0.0')

API

pack(secret, label)

The secret is bundled up with the label given to the secret and stringified as JSON

unpack(secret, version)

The secret is separated from the label and returned as an object

share(secret, numOfShards, quorum)

  • Generates a MAC which is composed the first 32 characters (16 bytes) of a SHA256 hash of the secret
  • Concatenates it at the beginning of the secret
  • Splits the secret into numOfShards, where quorum is the number required to reassemble
  • Compresses the shards from hex into base64 for more efficient storage

verify(shards, version)

  • Decompresses the shards from base64 to hex
  • Reassembles the secret
  • Checksig
    • MAC generated from the newly returned secret match the MAC attached to the returned secret.
    • Returns false if fails to pass check

combine(shards, version)

  • Decompresses the shards from base64 to hex
  • Reassembles the secret
  • Checksig
    • MAC generated from the newly returned secret match the MAC attached to the returned secret.
    • Throws an error if it fails to pass the check
  • Returns the JSON string secret

validateShard(shard, version)

  • Decompresses the shards from base64 to hex
  • Extracts components of the shard
    • bits: [Number] The number of bits configured when the share was created.
    • id: [Number] The ID number associated with the share when created.
    • data: [String] A hex string of the actual share data.