Added decryptMessage function for implementation eth_decryptMessage

README.md

@@ -61,7 +61,11 @@ You must return a valid signed ethereumjs-tx (https://github.com/ethereumjs/ethe
 
 ### signMessage(address, data)
 
-The `eth_sign` method will receive the incoming data, alread hashed, and must sign that hash, and then return the raw signed hash.
+The `eth_sign` method will receive the incoming data, already hashed, and must sign that hash, and then return the raw signed hash.
+
+### decryptMessage(address, data)
+
+The `eth_decryptMessage` method will receive the incoming data in array format that returns `encrypt` function in `eth-sig-util` and must decrypt message, and then return the raw message.
 
 ### exportAccount(address)
 

index.js

@@ -83,6 +83,15 @@ class SimpleKeyring extends EventEmitter {
     return Promise.resolve(sig)
   }
 
+  // For eth_decryptMessage:
+  decryptMessage (withAccount, encryptedData) {
+    const wallet = this._getWalletForAccount(withAccount)
+    const privKey = ethUtil.stripHexPrefix(wallet.getPrivateKey())
+    const privKeyBuffer = new Buffer(privKey, 'hex')
+    const sig = sigUtil.decrypt(encryptedData, privKey)
+    return Promise.resolve(sig)
+  }
+
   // personal_signTypedData, signs data along with the schema
   signTypedData (withAccount, typedData, opts = {}) {
     return this.signTypedData_v1(withAccount, typedData, opts);

test/index.js

@@ -309,6 +309,20 @@ describe('simple-keyring', () => {
       assert.equal(restored, address, 'recovered address')
     })
   })
+
+  describe('#decryptMessage', () => {
+    it('returns the expected value', async () => {
+      const address = '0xbe93f9bacbcffc8ee6663f2647917ed7a20a57bb'
+      const privateKey = new Buffer('6969696969696969696969696969696969696969696969696969696969696969', 'hex')
+      const privKeyHex = ethUtil.bufferToHex(privateKey)
+      const message = 'Hello world!'
+	  const encryptedMessage = sigUtil.encrypt(sigUtil.getEncryptionPublicKey(privateKey), {'data': message}, 'x25519-xsalsa20-poly1305')
+
+	  await keyring.deserialize([privKeyHex])
+      const decryptedMessage = await keyring.decryptMessage(address, encryptedMessage)
+      assert.equal(message, decryptedMessage, 'signature matches')
+    })
+  })
 
 
   describe('#signTypedData_v4 signature verification', () => {