Add basic multiproof generation and verification

src/baseTrie.js

@@ -72,6 +72,24 @@ module.exports = class Trie {
     })
   }
 
+  /**
+   * Generate a proof for multiple keys. Result is a de-duplicated set of
+   * trie nodes (in no particular order) which can be used to construct
+   * a partial trie.
+   */
+  static proveMultiple (trie, keys, cb) {
+    const proofNodes = {}
+    async.map(keys, (key, cb) => Trie.prove(trie, key, cb), (err, results) => {
+      if (err) return cb(err)
+      for (let proof of results) {
+        for (let node of proof) {
+          proofNodes[ethUtil.keccak256(node)] = node
+        }
+      }
+      return cb(null, Object.values(proofNodes))
+    })
+  }
+
   static verifyProof (rootHash, key, proofNodes, cb) {
     let proofTrie = new Trie(null, rootHash)
     Trie.fromProof(proofNodes, (error, proofTrie) => {
@@ -82,6 +100,14 @@ module.exports = class Trie {
     }, proofTrie)
   }
 
+  static verifyMultiproof (rootHash, keys, proofNodes, cb) {
+    let proofTrie = new Trie(null, rootHash)
+    Trie.fromProof(proofNodes, (err, proofTrie) => {
+      if (err) return cb(new Error('Invalid proof nodes given'), null)
+      async.map(keys, (k, cb) => proofTrie.get(k, cb), cb)
+    }, proofTrie)
+  }
+
   /**
    * Gets a value given a `key`
    * @method get

test/proof.js

@@ -238,3 +238,58 @@ tape('simple merkle proofs generation and verification', function (tester) {
     })
   })
 })
+
+tape('multiproof generation and verification', function (tester) {
+  var it = tester.test
+  it('create a multiproof and verify it', function (t) {
+    var trie = new Trie()
+
+    async.series([
+      function (cb) {
+        trie.put('key1aa', '0123456789012345678901234567890123456789xx', cb)
+      },
+      function (cb) {
+        trie.put('key2bb', 'aval2', cb)
+      },
+      function (cb) {
+        trie.put('key3cc', 'aval3', cb)
+      },
+      function (cb) {
+        Trie.proveMultiple(trie, ['key2bb', 'key3cc'], function (err, proofNodes) {
+          if (err) return cb(err)
+          Trie.verifyMultiproof(trie.root, ['key2bb', 'key3cc'], proofNodes, function (err, values) {
+            if (err) return cb(err)
+            t.equal(values.length, 2)
+            t.equal(values[0].toString('utf8'), 'aval2')
+            t.equal(values[1].toString('utf8'), 'aval3')
+            cb()
+          })
+        })
+      },
+      function (cb) {
+        Trie.proveMultiple(trie, ['nono', 'key3cc'], function (err, proofNodes) {
+          if (err) return cb(err)
+          Trie.verifyMultiproof(trie.root, ['nono', 'key3cc'], proofNodes, function (err, values) {
+            if (err) return cb(err)
+            t.equal(values.length, 2)
+            t.equal(values[0], null)
+            t.equal(values[1].toString('utf8'), 'aval3')
+            cb()
+          })
+        })
+      },
+      function (cb) {
+        // proof shouldn't work for different keys
+        Trie.proveMultiple(trie, ['key2bb', 'key3cc'], function (err, proofNodes) {
+          if (err) return cb(err)
+          Trie.verifyMultiproof(trie.root, ['key3cc', 'key1aa'], proofNodes, function (err, values) {
+            t.ok(err)
+            cb()
+          })
+        })
+      }
+    ], function (err) {
+      t.end(err)
+    })
+  })
+})