An electronic contract is a legally enforceable binding agreement that is entered into electronically, without signing a paper form. Electronic signatures take the place of handwritten signatures and are regularly used to sign electronic contracts. An electronic contract may be a user agreement that must be accepted in order to use computer software; in this case, users often are required to click a button signifying agreement to the terms of the contract. An electronic contract may also be a digital version of a formal contract, and a representational image of a signature may be used to sign the contract. Digital cryptography is also often used to authenticate signatures on electronic contracts. Both U.S. Federal and state laws exist to govern the use of electronic contracts. The Electronic Signatures in Global and National Commerce Act, also known as the E-Sign Act, gives legal validity to electronic contracts, ensuring that an electronic contract signed digitally is just as valid under the law as paper contracts.