feat(keys): implement generateKeyPairFromSeed for ed25519

Implement generateKeyPairFromSeed for ed25519 - this will produce the same keypair for the same seed (or first 32 bytes of reader) as given to GenerateKeyPairWithReader in go-libp2p.

src/crypto/ed25519.js

@@ -22,6 +22,22 @@ exports.generateKey = function (callback) {
   done(null, keys)
 }
 
+// seed should be a 32 byte uint8array
+exports.generateKeyFromSeed = function (seed, callback) {
+  const done = (err, res) => setImmediate(() => {
+    callback(err, res)
+  })
+
+  let keys
+  try {
+    keys = nacl.sign.keyPair.fromSeed(seed)
+  } catch (err) {
+    done(err)
+    return
+  }
+  done(null, keys)
+}
+
 exports.hashAndSign = function (key, msg, callback) {
   setImmediate(() => {
     callback(null, Buffer.from(nacl.sign.detached(msg, key)))

src/index.js

@@ -30,6 +30,19 @@ exports.generateKeyPair = (type, bits, cb) => {
   key.generateKeyPair(bits, cb)
 }
 
+// Generates a keypair of the given type and bitsize
+// seed is a 32 byte uint8array
+exports.generateKeyPairFromSeed = (type, seed, bits, cb) => {
+  let key = keys[type.toLowerCase()]
+  if (!key) {
+    return cb(new Error('invalid or unsupported key type'))
+  }
+  if (type.toLowerCase() !== 'ed25519') {
+    return cb(new Error('Seed key derivation is unimplemented for RSA or secp256k1'))
+  }
+  key.generateKeyPairFromSeed(seed, bits, cb)
+}
+
 // Converts a protobuf serialized public key into its
 // representative object
 exports.unmarshalPublicKey = (buf) => {

src/keys/ed25519.js

@@ -117,6 +117,27 @@ function generateKeyPair (_bits, cb) {
   })
 }
 
+function generateKeyPairFromSeed (seed, _bits, cb) {
+  if (cb === undefined && typeof _bits === 'function') {
+    cb = _bits
+  }
+
+  crypto.generateKeyFromSeed(seed, (err, keys) => {
+    if (err) {
+      return cb(err)
+    }
+    let privkey
+    try {
+      privkey = new Ed25519PrivateKey(keys.secretKey, keys.publicKey)
+    } catch (err) {
+      cb(err)
+      return
+    }
+
+    cb(null, privkey)
+  })
+}
+
 function ensure (cb) {
   if (typeof cb !== 'function') {
     throw new Error('callback is required')
@@ -138,5 +159,6 @@ module.exports = {
   Ed25519PrivateKey,
   unmarshalEd25519PrivateKey,
   unmarshalEd25519PublicKey,
-  generateKeyPair
+  generateKeyPair,
+  generateKeyPairFromSeed
 }

test/ed25519.spec.js

@@ -35,6 +35,70 @@ describe('ed25519', () => {
     })
   })
 
+  it('generates a valid key from seed', (done) => {
+    var seed = crypto.randomBytes(32)
+    crypto.generateKeyPairFromSeed('Ed25519', seed, 512, (err, seededkey) => {
+      if (err) return done(err)
+      expect(
+        seededkey
+      ).to.be.an.instanceof(
+        ed25519.Ed25519PrivateKey
+      )
+
+      seededkey.hash((err, digest) => {
+        if (err) {
+          return done(err)
+        }
+
+        expect(digest).to.have.length(34)
+        done()
+      })
+    })
+  })
+
+  it('generates the same key from the same seed', (done) => {
+    var seed = crypto.randomBytes(32)
+    crypto.generateKeyPairFromSeed('Ed25519', seed, 512, (err, seededkey1) => {
+      if (err) return done(err)
+      crypto.generateKeyPairFromSeed('Ed25519', seed, 512, (err, seededkey2) => {
+        if (err) return done(err)
+        expect(
+          seededkey1.equals(seededkey2)
+        ).to.be.eql(
+          true
+        )
+        expect(
+          seededkey1.public.equals(seededkey2.public)
+        ).to.be.eql(
+          true
+        )
+        done()
+      })
+    })
+  })
+
+  it('generates different keys for different seeds', (done) => {
+    var seed1 = crypto.randomBytes(32)
+    crypto.generateKeyPairFromSeed('Ed25519', seed1, 512, (err, seededkey1) => {
+      if (err) return done(err)
+      var seed2 = crypto.randomBytes(32)
+      crypto.generateKeyPairFromSeed('Ed25519', seed2, 512, (err, seededkey2) => {
+        if (err) return done(err)
+        expect(
+          seededkey1.equals(seededkey2)
+        ).to.be.eql(
+          false
+        )
+        expect(
+          seededkey1.public.equals(seededkey2.public)
+        ).to.be.eql(
+          false
+        )
+        done()
+      })
+    })
+  })
+
   it('signs', (done) => {
     const text = crypto.randomBytes(512)