Cryptography – How to Think About the Permanence of Cryptographically Signed Messages

cryptographymetamasksignature

I'm making a couple of assumptions about signing messages from an ethereum wallet (Metamask), like the one in the screenshot:

"By default" — without extra work on the part of 1inch — no record of my signing this message will appear on-chain
If they wanted to or were forced to, 1inch could put this information on-chain: they could provably record the fact that the private key associated with my ethereum address signed this message

Please let me know if either assumption is wrong. Thanks!

(PS: to any US authorities reading this, I'm asking this question for journalistic purposes and will say so under oath 🙂)

Best Answer

Both of your assumptions are correct. Message signing happens off chain, and is in fact required in order to send a transaction on the chain (through signing a transaction).

To put a message on chain, you (or 1inch, ...) needs to actively send a transaction on chain including the signed message. A message signature is essentially just some binary data, so 1inch could put this on chain (together with the message hash) if they wanted to. Others would then be able to see who signed the message, by recovering the signer from the signature, and thus verify if your address signed the message.

Related Solutions

[Ethereum] Should signed text messages use the “\x19Ethereum Signed Message” prefix

There's no official standard (at the time of this writing) and has been debated for a while in this EIP thread EIP #683

According to issue #3731:

Geth prepends the string \x19Ethereum Signed Message:\n<length of message> to all data before signing it (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign). If you want to verify such a signature from Solidity, you'll have to prepend the same string in solidity before doing the ecrecovery.

signature – How to Extract v, r, s Values from a Signed Transaction

This part of the signed transaction contains the v, r, and s fields:

25a028ef61340bd939bc2195fe537567866003e1a15d3c71ff63e1590620aa636276a067cbe9d8997f761aecb703304b3800ccf555c9f3dc64214b297fb1966a3b6d83

We can go through each byte (One byte is two characters in the above transaction)

The values are:

v=0x25=37

r_length=(0xa0-0x80)=0x20=32 (bytes)

r=0x28ef61340bd939bc2195fe537567866003e1a15d3c71ff63e1590620aa636276

s_length=0xa0-0x80=32

s=0x67cbe9d8997f761aecb703304b3800ccf555c9f3dc64214b297fb1966a3b6d83

The encoding of an Ethereum transaction is called RLP and you can find the find it definition in the Ethereum Yellow Paper.

Best Answer

Related Solutions

[Ethereum] Should signed text messages use the “\x19Ethereum Signed Message” prefix

signature – How to Extract v, r, s Values from a Signed Transaction

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