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.
Prepress proofing. A contract proof usually serves as an agreement between customer and printer and as a color reference guide for adjusting the press before the final press run. Most contract proofs are a prepress proof. The primary goal of 'proofing' is to serve as a tool for customer verification that the entire job is accurate. Prepress proofing (also known as off-press proofing) is a cost-effective way of providing a visual copy without the expense of creating a press proof.