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dag-jose

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This library provides a TypeScript implementation of the DAG-JOSE codec for IPLD.

It supports the new multiformats library in order to be compatible with both the current and future js-ipfs implementations.

To create and work with DAG-JOSE compatible JOSE objects we recommend using the dag-jose-utils library.

JWS Signing Usage

The following example is available in complete form in example-signing-ipld.mjs.

For independent usage as an IPLD codec:

import * as Block from 'multiformats/block'
import { sha256 } from 'multiformats/hashes/sha2'
import * as dagCbor from '@ipld/dag-cbor' // for decoding the signed payload
import * as dagJose from 'dag-jose'

Import additional libraries for JWS handling:

// JWT & utilities
import {
  ES256KSigner,
  createJWS,
  verifyJWS
} from 'did-jwt'
import {
  encodePayload,
  toJWSPayload,
  toJWSStrings
} from 'dag-jose-utils'

Given a keypair:

const pubkey = '03fdd57adec3d438ea237fe46b33ee1e016eda6b585c3e27ea66686c2ea5358479'
const privkey = '278a5de700e29faae8e40e366ec5012b5ec63d36ec77e8a2417154cc1d25383f'

Create a signed envelope block:

const signer = ES256KSigner(privkey)
// arbitrary data to DAG-CBOR encode, we get a:
// { cid:CID, linkedBlock: Uint8Array }
const payloadBlock = await encodePayload(payload)
// sign the CID as a JWS using our signer
const jws = await createJWS(toJWSPayload(payloadBlock), signer)

// createJWS gives us a compact string form JWS, DAG-JOSE will accept both the
// compact and general (object) form but a round-trip decode will always
// result in the general form. If we want need `jws` to be isometric regardless
// of whether it has been round-tripped through DAG-JOSE or straight out of
// `createJWS()` we can call `toGeneral()` to ensure it is always in the
// general form.
// jws = dagJose.toGeneral(jws)

// encode as a DagJWS IPLD block
const jwsBlock = await Block.encode({ value: jws, codec: dagJose, hasher: sha256 })

// we now have two blocks, a signed envelope and a payload
// DagJWS envelope:
//  - CID: jwsBlock.cid
//  - Bytes: jwsBlock.bytes
// Payload:
//  - CID: payloadBlock.cid
//  - Bytes: payloadBlock.linkedBlock

Given a DagJWS envelope block CID, load its bytes, verify the signature and load the linked payload block:

// validate cid matches bytes and decode dag-jose JWS
const jwsBlock = await Block.create({ bytes, cid, codec: dagJose, hasher: sha256 })
const jwsStrings = toJWSStrings(jwsBlock.value)
// verify the signatures found in the block against our pubkey
for (const jws of jwsStrings) {
  const verifiedKey = verifyJWS(jws, [{ publicKeyHex: pubkey }]) // will throw if it doesn't verify
  console.log(`Verified JWS envelope \u001b[32m${cid}\u001b[39m with public key:\n\t${verifiedKey.publicKeyHex}`)
}

const payloadCid = jwsBlock.value.link
// `store.get()` represents a block store, where `get(cid:string):Uint8Array`,
// in this example case it's simply a `Map` but it could be any method of
// fetching bytes for a CID
const payloadBytes = store.get(payloadCid.toString())
// validate payloadCid matches bytes and decode dag-cbor payload
const payloadBlock = await Block.create({ bytes: payloadBytes, cid: payloadCid, codec: dagCbor, hasher: sha256 })

// The signed and verified payload is available in `payloadBlock.value`

JWE Encryption Usage

When using DAG-JOSE (for JWE or JWS) with js-IPFS, you will need to convert it from a raw multiformats style codec to a legacy IPLD codec using blockcodec-to-ipld-format.

The following example is available in complete form in example-ipfs.mjs.

A plain IPLD (without IPFS, for cases where you are managing the block store) version is available in example-ipld.mjs.

// IPLD & IPFS
import { create as createIpfs } from 'ipfs'
import { convert as toLegacyIpld } from 'blockcodec-to-ipld-format'

import * as dagJose from 'dag-jose'

// JWT & utilities
import {
  xc20pDirEncrypter,
  xc20pDirDecrypter,
  x25519Encrypter,
  x25519Decrypter,
  decryptJWE,
  createJWE
} from 'did-jwt'
import {
  decodeCleartext,
  prepareCleartext
} from 'dag-jose-utils'

// Miscellaneous crypto libraries to support the examples
import { randomBytes } from '@stablelib/random'
import { generateKeyPairFromSeed } from '@stablelib/x25519'

Set up js-IPFS:

const dagJoseIpldFormat = toLegacyIpld(dagJose)

// Async setup tasks
async function setup () {
  console.log('Starting IPFS ...')
  // Instantiate an IPFS node, that knows how to deal with DAG-JOSE blocks
  ipfs = await createIpfs({ ipld: { formats: [dagJoseIpldFormat] } })
}

Symmetric encryption

Encrypt and store a payload using a secret key:

const storeEncrypted = async (payload, key) => {
  const dirEncrypter = xc20pDirEncrypter(key)
  // prepares a cleartext object to be encrypted in a JWE
  const cleartext = await prepareCleartext(payload)
  // encrypt into JWE container layout using secret key
  const jwe = await createJWE(cleartext, [dirEncrypter])
  // let IPFS store the bytes using the DAG-JOSE codec and return a CID
  const cid = await ipfs.dag.put(jwe, { format: dagJoseIpldFormat.codec, hashAlg: 'sha2-256' })
  console.log(`Encrypted block CID: \u001b[32m${cid}\u001b[39m`)
  return cid
}

Load an encrypted block from a CID and decrypt the payload using a secret key:

const loadEncrypted = async (cid, key) => {
  const dirDecrypter = xc20pDirDecrypter(key)
  const retrieved = await ipfs.dag.get(cid)
  const decryptedData = await decryptJWE(retrieved.value, dirDecrypter)
  return decodeCleartext(decryptedData)
}

Create a key, encrypt and store a block, then load and decrypt it:

const key = randomBytes(32)
const secretz = { my: 'secret message' }
console.log('Encrypting and storing secret:\u001b[1m', secretz, '\u001b[22m')
const cid = await storeEncrypted(secretz, key)
const decoded = await loadEncrypted(cid, key)
console.log('Loaded and decrypted block content:\u001b[1m', decoded, '\u001b[22m')

Asymmetric encryption

Encrypt and store a payload using a public key:

const storeEncrypted = async (payload, pubkey) => {
  const asymEncrypter = x25519Encrypter(pubkey)
  // prepares a cleartext object to be encrypted in a JWE
  const cleartext = await prepareCleartext(payload)
  // encrypt into JWE container layout using public key
  const jwe = await createJWE(cleartext, [asymEncrypter])
  // let IPFS store the bytes using the DAG-JOSE codec and return a CID
  const cid = await ipfs.dag.put(jwe, { format: dagJoseIpldFormat.codec, hashAlg: 'sha2-256' })
  console.log(`Encrypted block CID: \u001b[32m${cid}\u001b[39m`)
  return cid
}

Load an encrypted block from a CID and decrypt the payload using a secret key:

const loadEncrypted = async (cid, privkey) => {
  const asymDecrypter = x25519Decrypter(privkey)
  // decode the DAG-JOSE envelope
  const retrieved = await ipfs.dag.get(cid)
  const decryptedData = await decryptJWE(retrieved.value, asymDecrypter)
  return decodeCleartext(decryptedData)
}

Create a key pair, encrypt and store a block using the public key, then load and decrypt it using the private key:

const privkey = randomBytes(32)
// generate a public key from the existing private key
const pubkey = generateKeyPairFromSeed(privkey).publicKey
const secretz = { my: 'secret message' }
console.log('Encrypting and storing secret with public key:\u001b[1m', secretz, '\u001b[22m')
const cid = await storeEncrypted(secretz, pubkey)
const decoded = await loadEncrypted(cid, privkey)
console.log('Loaded and decrypted block content with private key:\u001b[1m', decoded, '\u001b[22m')

Encrypt and decrypt using other jose library

The did-jwt library only supports x25519 key exchange and XChacha20Poly1305. If you want to use the dag-jose codec with other less secure algorithms you can encrypt another library and put the resulting JWE into the dag. Below is an example using the jose library.

const jwk = jose.JWK.generateSync('oct', 256)
const cleartext = prepareCleartext({ my: 'secret message' })

// encrypt and put into ipfs
const jwe = jose.JWE.encrypt.flattened(cleartext, jwk, { alg: 'dir', enc: 'A128CBC-HS256' })
const cid = await ipfs.dag.put(jwe, { format: format.codec, hashAlg: 'sha2-256' })

// retreive and decrypt object
const retrived = await ipfs.dag.get(cid)
const decryptedData = jose.JWE.decrypt(retrived, jwk)
console.log(decodeCleartext(decryptedData))
// output:
// { my: 'secret message' }

Maintainer

Joel Thorstensson

License

FOSSA Status