Add docs

Author: ernestognw

docs/modules/ROOT/pages/utilities.adoc

@@ -34,3 +34,28 @@ In case your smart contract validates signatures, using xref:api:utils.adoc#ERC7
 ----
 include::api:example$utils/cryptography/ERC7739SignerECDSA.sol[]
 ----
+
+==== ERC-7913 Signature Verifiers
+
+ERC-7913 extends the concept of signature verification to support keys that don't have their own Ethereum address. This is particularly useful for integrating non-Ethereum cryptographic curves, hardware devices, or other identity systems into smart accounts.
+
+The standard defines a verifier interface that can be implemented to support different types of keys. A signer is represented as a `bytes` object that concatenates a verifier address and a key: `verifier || key`.
+
+xref:api:utils.adoc#ERC7913Utils[`ERC7913Utils`] provides functions for verifying signatures using ERC-7913 compatible verifiers:
+
+[source,solidity]
+----
+using ERC7913Utils for bytes;
+
+function _verify(bytes memory signer, bytes32 hash, bytes memory signature) internal view returns (bool) {
+    return signer.isValidSignatureNow(hash, signature);
+}
+----
+
+The verification process works as follows:
+
+* If `signer.length < 20`: verification fails
+* If `signer.length == 20`: verification is done using https://docs.openzeppelin.com/contracts/5.x/api/utils#SignatureChecker[SignatureChecker]
+* Otherwise: verification is done using an ERC-7913 verifier.
+
+This allows for backward compatibility with EOAs and ERC-1271 contracts while supporting new types of keys.