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`.
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.
