feat: crypto errors (#4)

* chore: ignore docs folder

* feat: add invalid crypto exchange error

src/crypto/README.md

@@ -84,6 +84,7 @@ Common crypto errors come with the interface, and can be imported directly. All
 
 ```js
 const {
+  InvalidCryptoExchangeError,
   UnexpectedPeerError
 } = require('libp2p-interfaces/src/crypto/errors')
 
@@ -93,4 +94,5 @@ console.log(error.code === UnexpectedPeerError.code) // true
 
 ### Error Types
 
-- `UnexpectedPeerError` - Should be thrown when the expected peer id does not match the peer id determined via the crypto exchange
+- `InvalidCryptoExchangeError` - Should be thrown when a peer provides data that is insufficient to finish the crypto exchange.
+- `UnexpectedPeerError` - Should be thrown when the expected peer id does not match the peer id determined via the crypto exchange.

src/crypto/errors.js

@@ -11,6 +11,18 @@ class UnexpectedPeerError extends Error {
   }
 }
 
-module.exports = {
-  UnexpectedPeerError
+class InvalidCryptoExchangeError extends Error {
+  constructor (message = 'Invalid crypto exchange') {
+    super(message)
+    this.code = InvalidCryptoExchangeError.code
+  }
+
+  static get code () {
+    return 'ERR_INVALID_CRYPTO_EXCHANGE'
+  }
+}
+
+module.exports = {
+  UnexpectedPeerError,
+  InvalidCryptoExchangeError
 }