Make Crypto contract compatible with Ethereum

[turbolent]

Issue To Be Solved

It would be nice to verify Ethereum signatures in a Cadence contract.

Suggested Solution

• Add Keccak hashing algorithm
• Allow providing a custom tag, e.g. the Ethereum personal signed message prefix

[KSlashh]

We need keccak256 !

[KSlashh]

To deal with cross chain message from EVM compatible chain, keccak256 is necessary.

[btspoony]

To deal with cross chain message from EVM compatible chain, keccak256 is necessary.

I think there are two things we are missing:

1. keccak256 Hash Algorithm support
2. a recover function for keys using ECDSA Algorithm , since EVM Tx only have signature and recoverId

[superdcc]

We need keccak256 !

[turbolent]

Adding the Keccak256 hash algorithm was requested in #1326 and implemented in #1327

[turbolent]

Is there still a need for a custom tag? cc @tarakby

[tarakby]

@turbolent custom tags can be used when verifying ECDSA signatures so I guess you can tick the second item of the issue.

[turbolent]

@tarakby Sounds good! Does that mean we can close the issue as done?

[tarakby]

Yes, enabling Keccak and custom tags is done (the items on the issue description). However this doesn't mean the crypto of Cadence is totally compatible with Ethereum (title of the issue) because the equivalent of ecrecover isn't supported by Cadence.
We could close this issue and ecrecover can be the subject of another issue.