Create EIP 191 (#973)

EIPS/eip-191.md

@@ -0,0 +1,63 @@
+---
+eip: 191
+title: Signed Data Standard
+authors: Martin Holst Swende (@holiman), Nick Johnson <arachnid@notdot.net>
+Status: Draft
+Type: Standards Track
+Category: ERC
+Created: 2016-01-20
+---
+
+# Abstract
+
+This ERC proposes a specification about how to handle signed data in Etherum contracts.
+
+# Motivation
+
+Several multisignature wallet implementations have been created which accepts `presigned` transactions. A `presigned` transaction is a chunk of binary `signed_data`, along with signature (`r`, `s` and `v`). The interpretation of the `signed_data` has not been specified, leading to several problems:
+
+* Standard Ethereum transactions can be submitted as `signed_data`. An Ethereum transaction can be unpacked, into the following components: `RLP<nonce, gasPrice, startGas, to, value, data>` (hereby called `RLPdata`), `r`, `s` and `v`. If there are no syntactical constraints on `signed_data`, this means that `RLPdata` can be used as a syntactically valid `presigned` transaction.
+* Multisignature wallets have also had the problem that a `presigned` transaction has not been tied to a particular `validator`, i.e a specific wallet. Example:
+    1. Users `A`, `B` and `C` have the `2/3`-wallet `X`
+    2. Users `A`, `B` and `D` have the `2/3`-wallet `Y`
+    3. User `A` and `B` submites `presigned` transaction to `X`.
+    4. Attacker can now reuse their presigned transactions to `X`, and submit to `Y`.
+
+## Specification
+
+We propose the following format for `signed_data`
+
+```
+0x19 <1 byte version> <version specific data> <data to sign>.
+```
+Version `0` has `<20 byte address>` for the version specific data, and the `address` is the intended validator. In the case of a Multisig wallet, that is the wallet's own address  .
+
+The initial `0x19` byte is intended to ensure that the `signed_data` is not valid [RLP](https://github.com/ethereum/wiki/wiki/RLP)
+
+> For a single byte whose value is in the [0x00, 0x7f] range, that byte is its own RLP encoding.
+
+That means that any `signed_data` cannot be one RLP-structure, but a 1-byte `RLP` payload followed by something else. Thus, any ERC-191 `signed_data` can never be an Ethereum transaction.
+
+Additionally, `0x19` has been chosen because since ethereum/go-ethereum#2940 , the following is prepended before hashing in personal_sign:
+
+```
+"\x19Ethereum Signed Message:\n" + len(message).
+```
+
+Using `0x19` thus makes it possible to extend the scheme by defining a version `0x45` (`E`) to handle these kinds of signatures.
+
+### Example
+
+    function submitTransactionPreSigned(address destination, uint value, bytes data, uint nonce, uint8 v, bytes32 r, bytes32 s)
+        public
+        returns (bytes32 transactionHash)
+    {
+       // Arguments when calculating hash to validate
+        // 1: byte(0x19) - the initial 0x19 byte
+        // 2: byte(0) - the version byte
+        // 4: this - the validator address
+        // 4-7 : Application specific data
+        transactionHash = keccak256(byte(0x19),byte(0),this,destination, value, data, nonce);
+        sender = ecrecover(transactionHash, v, r, s);
+        // ...
+    }