EIP-1707: Use Version Byte Prefix for Contract Account Versioning

EIPS/eip-1707.md

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+---
+eip: 1707
+title: Use Version Byte Prefix for Contract Account Versioning
+author: Wei Tang (@sorpaas)
+discussions-to: https://github.com/sorpaas/EIPs/issues/3
+status: Abandoned
+type: Standards Track
+category: Core
+superseded-by: 1702
+created: 2019-01-17
+---
+
+## Simple Summary
+
+Provide an alternative proposal compared with EIP-1702 / ECIP-1040,
+with the following advantages:
+
+* We don't need to modify existing account state format.
+* We don't need to modify how precompiled contracts are invoked.
+* Compatible with the standard WebAssembly binary format.
+
+## Specification
+
+After `FORK_BLOCK`, before an account or contract creation transaction
+code is executed, check that whether:
+
+* The first byte is `\0` (`0x00`).
+* The code length is greater or equal to 4.
+
+If so, we define the second to fourth bytes as version bits. Instead
+of executing on the default EVM, pass the *whole* code array to a VM
+defined by the version bits.
+
+* If version bytes are `\0\0\1`, then invoke "EVM1", where the first 4
+  bytes are stripped, and the rest of the code bytes are executed in
+  an EVM with "EVM1" config.
+* If version bytes are `asm`, then invoke WebAssembly virtual
+  machine. This is compatible with the standard WebAssembly binary
+  format because it always starts with `\0asm`.
+
+If the above does not match, execute it on the default EVM. Note that
+if the first byte is `\0`, the client can short circuit and stop
+immediately.
+
+## Copyright
+
+Copyright and related rights waived via
+[CC0](https://creativecommons.org/publicdomain/zero/1.0/).