With secret key cryptography, a single key is used for both encryption and decryption. As shown in Figure the sender uses the key (or some set of rules) to encrypt the plain text and sends the ciphertext to the receiver. The receiver applies the same key (or ruleset) to decrypt the message and recover the plain text.
Proofreading means examining your text carefully to find and correct typographical errors and mistakes in grammar, style, and spelling. Usually, for those who do not have time, they hire a professional proofreaders to help them do it. Before You Proofread: Set your text aside for a while (15 minutes, a day, a week) between writing and proofing. Some distance from the text will help you see mistakes more easily.
The certification by a custodian of records that a copy of an original document is a true copy that is demonstrated by his or her signature on a certificate. An attestation is a declaration by a witness that an instrument has been executed in his or her presence according to the formalities required by law. It is not the same as an Acknowledgment, a statement by the maker of a document that verifies its authenticity.