If both Party A and Party B are legal persons, and the contract clearly stipulates that the legal person's seal and the legal representative's signature are required for both parties to take effect, the legal person's seal is also required. If there is no agreement in the contract, if the electronic signature conforms to the relevant provisions of the Electronic Signature Law and is true and valid, the contract is valid.

According to Article 11 of the Contract Law, contracts signed by fax are also valid. Article 11 Written forms refer to forms such as contracts, letters and data messages (including telegrams, telexes, faxes, electronic data interchange and e-mails) that can tangibly express the contents contained.

According to the provisions of the Electronic Signature Law: Article 13 An electronic signature that meets the following conditions shall be regarded as reliable:

1. When electronic signature production data is used for electronic signature, it belongs to the electronic signer.

2. When signing, the electronic signature production data is only controlled by the electronic signer.

3. Any changes to the electronic signature after signing can be found.

Any changes in the content and form of the data message after signing can be found. The parties can also choose to use electronic signatures that meet their agreed reliable conditions.

Article 14 A reliable electronic signature has the same legal effect as a handwritten signature or seal. Article 16 Where an electronic signature requires authentication by a third party, a legally established electronic authentication service provider shall provide authentication services.

The second paragraph of Article 280 of China's Criminal Law stipulates the crime of forging company seals: "Whoever forges the seals of companies, enterprises, institutions or people's organizations shall be sentenced to fixed-term imprisonment of not more than three years, criminal detention, public surveillance or deprivation of political rights."