Account Abstraction - Custom Validation Signature Scheme

listings/advanced-concepts/custom_signature_validation/src/custom_signature.cairo

@@ -1,3 +1,4 @@
+// ANCHOR: custom_signature_scheme
 use starknet::secp256_trait::{
     Secp256PointTrait, Signature as Secp256Signature, recover_public_key, is_signature_entry_valid
 };
@@ -131,3 +132,4 @@ impl U256TryIntoSignerType of TryInto<u256, SignerType> {
     }
 }
 
+// ANCHOR_END: custom_signature_scheme

src/advanced-concepts/custom_signature_validation.md

@@ -1,17 +1,38 @@
 # Custom Signature Validation Scheme
 
-Account Abstraction on Starknet supports various signature schemes. This means that signature schemes on Starknet are not limited to just one, any standard signature scheme can be validated, for example Starknet signature, Secp256k1, Secp256r1, Eip191 et al are some of the custom signatures that can be validated on Starknet currently. 
+Account Abstraction is a native feature on Starknet, this makes it possible for anyone to implement custom signature schemes. The implication is that signature schemes on Starknet are not limited to just one, any standard signature scheme can be validated, for example Starknet signature, Secp256k1, Secp256r1, Eip191 etc are some of the custom signatures that can be validated on Starknet currently. 
 
 ### The Concepts of Accounts and Signers
 
-i. **Account:** All accounts are smart contracts that can hold assets and execute transactions on Starknet protocol, these account contracts however must implement some specific methods outlined in SNIP-6.
+i. **Account:** All accounts are smart contracts that can hold assets and execute transactions on Starknet, these account contracts however must implement some specific methods outlined in SNIP-6. For further reading: [Account contract](https://starknet-by-example.voyager.online/advanced-concepts/account_abstraction/account_contract.html).
 
 ii. **Signers:** These are responsible for digitally signing transactions and provide the authorization needed to initiate transactions. 
 Digital signatures are cryptographic proofs that transactions are authorized by corresponding accounts.
 
-In summary, Starknet accounts are normal blockchain accounts that hold assets and initiate transactions onchain, while signers provide the authorization required to ensure that transactions originating from these accounts are secure, valid and executed.
+### Signature validation on Starknet
 
-To implement custom validation method on Starknet you have to ensure that the contract contains these three methods: `is_valid_signature`, `__validate__` and `__execute__`. These are the building block for account contracts on Starknet as contained in the SNIP-6.
+On Starknet transactions are signed offchain, which means that the signature process happens outside the blockchain. The signed transaction is then submitted to Starknet network for verification and execution. Read more: [Starknet-js docs](https://www.starknetjs.com/docs/guides/signature/)
 
+All Account contracts on Starknet must implement the SNIP-6 standard as mentioned earlier. The methods implemented in the SNIP-6 standard provide means to move offchain signatures onchain and execute them.
 
+`is_valid_signature` returns true if the signature is valid, `__validate__` validates the signature and marks them as 'VALIDATED', while `__execute__` executes the validated transaction. Sample implementation of SNIP-6 standard: [Sample SNIP-6 Implementation](https://starknet-by-example.voyager.online/advanced-concepts/account_abstraction/account_contract.html#minimal-account-contract-executing-transactions)
 
+
+On Ethereum, EOAs directly sign transactions onchain using their private keys. This onchain signing of transactions is more secure and straightforward but less flexible. Offchain signing employed on Starknet gives room for more flexibility aside the ability to implement custom signature schemes, however, care must be taken to validate all signatures meticulously to ensure that:
+
+a. the message has not been altered.
+b. the signer owns the private key corresponding to the public key.
+
+
+In summary, Starknet accounts are normal blockchain accounts that hold assets and initiate transactions onchain, while signers provide the authorization required to ensure that transactions originating from these accounts are secure and valid.
+
+Digital signatures are a fundamental aspect of modern cryptography, used to verify the authenticity and integrity of digital messages or transactions. They are based on public-key cryptography, where a pair of keys (a public key and a private key) are used to create and verify signatures.
+Private keys are kept secret and secure by the owner, and are used to sign the message or transaction, while the public key can be used by anyone to verify the signature.
+
+### Custom signature validation sample
+
+The example below shows a sample implementation of `Secp256r1` and `Secp256k1` signature schemes:
+
+```rust
+{{#rustdoc_include ../../listings/advanced-concepts/custom_signature_validation/src/custom_signature.cairo:custom_signature_scheme}}
+```