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---
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eip: 155
title: Simple replay attack protection
author: Vitalik Buterin
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type: Standards Track
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category: Core
status: Final
created: 2016-10-14
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---
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### Hard fork
[Spurious Dragon ](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-607.md )
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### Parameters
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- `FORK_BLKNUM` : 2,675,000
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- `CHAIN_ID` : 1 (main net)
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### Specification
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If `block.number >= FORK_BLKNUM` and `v = CHAIN_ID * 2 + 35` or `v = CHAIN_ID * 2 + 36` , then when computing the hash of a transaction for purposes of signing or recovering, instead of hashing only the first six elements (i.e. nonce, gasprice, startgas, to, value, data), hash nine elements, with `v` replaced by `CHAIN_ID` , `r = 0` and `s = 0` . The currently existing signature scheme using `v = 27` and `v = 28` remains valid and continues to operate under the same rules as it does now.
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### Example
Consider a transaction with `nonce = 9` , `gasprice = 20 * 10**9` , `startgas = 21000` , `to = 0x3535353535353535353535353535353535353535` , `value = 10**18` , `data=''` (empty).
The "signing data" becomes:
```
0xec098504a817c800825208943535353535353535353535353535353535353535880de0b6b3a764000080018080
```
The "signing hash" becomes:
```
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0xdaf5a779ae972f972197303d7b574746c7ef83eadac0f2791ad23db92e4c8e53
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```
If the transaction is signed with the private key `0x4646464646464646464646464646464646464646464646464646464646464646` , then the v,r,s values become:
```
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(37, 18515461264373351373200002665853028612451056578545711640558177340181847433846, 46948507304638947509940763649030358759909902576025900602547168820602576006531)
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```
Notice the use of 37 instead of 27. The signed tx would become:
```
0xf86c098504a817c800825208943535353535353535353535353535353535353535880de0b6b3a76400008025a028ef61340bd939bc2195fe537567866003e1a15d3c71ff63e1590620aa636276a067cbe9d8997f761aecb703304b3800ccf555c9f3dc64214b297fb1966a3b6d83
```
### Rationale
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This would provide a way to send transactions that work on Ethereum without working on ETC or the Morden testnet. ETC is encouraged to adopt this EIP but replacing `CHAIN_ID` with a different value, and all future testnets, consortium chains and alt-etherea are encouraged to adopt this EIP replacing `CHAIN_ID` with a unique value.
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### List of Chain ID's:
| `CHAIN_ID` | Chain(s) |
| ---------------| -------------------------------------------|
| 1 | Ethereum mainnet |
| 2 | Morden (disused), Expanse mainnet |
| 3 | Ropsten |
| 4 | Rinkeby |
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| 8 | Ubiq mainnet |
| 9 | Ubiq testnet |
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| 30 | Rootstock mainnet |
| 31 | Rootstock testnet |
| 42 | Kovan |
| 61 | Ethereum Classic mainnet |
| 62 | Ethereum Classic testnet |
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| 66 | ewasm testnet |
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| 1337 | Geth private chains (default) |
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| 6284 | Görli |
| 314158 | Stureby |
