# is_evm_signatures_authorized_operation · FT4 Rell API · Chromia Docs (concept)

> function is_ evm_ signatures_ authorized_ operation(name: text): boolean Checks whether evm_signatures operation can be used with provided operation. We do

Source: https://docs.chromia.com/pages/ft4-rell/-f-t4-library/lib.ft4.core.auth/is_evm_signatures_authorized_operation/

FUNCTION

# is\_evm\_signatures\_authorized\_operation

```signature
function is_evm_signatures_authorized_operation(name: text): boolean
```

[Source](https://gitlab.com/chromaway/ft4-lib/-/blob/development/rell/src/lib/ft4/core/auth/module.rell#lines-452)

Checks whether `evm_signatures` operation can be used with provided operation.

We don't keep track of nonce for keys used with `evm_signatures`, therefore if not used with
care, authorizing an operation with `evm_signatures` could lead to replay attack.

In order to use it with an operation, the operation has to be whitelisted.
By default, library only allows `evm_signatures` to be used with certain operations.

`evm_signatures` is safe to use in combination with `ft_auth` or `evm_auth` operation.

However, if used as only way to authorize an operation, the operation has to ensure that it
cannot be called more than once with same parameters.

One way to avoid that is if the operation creates an entity that has some `key` value
that is derived from operation parameters.

Throws `"EVM SIG PARSING ERROR"` if the `chromia.yml` cannot be parsed for this parameter,
e.g. if some elements are not text or there are duplicates.

**Parameters**

* **name** — the operation to check

**See Also**

* [module\_args.evm\_signatures\_authorized\_operations](https://docs.chromia.com/pages/ft4-rell/-f-t4-library/lib.ft4.core.auth/module_args/) — for the whitelist

[View this page on docs.chromia.com](https://docs.chromia.com/pages/ft4-rell/-f-t4%20-library/lib.ft4.core.auth/is_evm_signatures_authorized_operation.html)Generated API reference, mirrored from the live docs