A document or file may be digitally signed using a party’s private signature key, creating a “digital signature” that is stored with the document. Anyone can validate the signature on the document using the public key from the digital certificate issued to the signer. Validating the digital signature confirms who signed it, and ensures that no alterations have been made to the document since it was signed. Similarly, an email message may be digitally signed using commonly available client software that implements an open standard for this purpose, such as Secure Multipurpose Internet Mail Extensions (S/MIME). Validating the signature on the email can help the recipient know with confidence who sent it, and that it was not altered during transmission. See Certificate..”