What is the minimum required functionality to roll your own e-signature which would be LEGALLY BINDING under the e-sign act? Seems all we need is: Consent to

What is the minimum required functionality to roll your own e-signature which would be LEGALLY BINDING under the e-sign act? Seems all we need is: Consent to do business electronically — All parties must agree to conduct transactions electronically, either explicitly or implied. Intent to sign — E-signatures are only valid if the signer intended to sign. Signature requests need to be declinable. Association of signature with the record — Signers must make a visible mark or statement on the e-document. Attribution — Whether a name or a unique mark, the signature must be attributable to the person signing and only linked to them. Record retention — Signed electronic documents must be saved, viewed, or printed by either party and stored for future reference.