From our earlier example in the section “The One-Way Hash,” if Kevin wants to ensure that the message he sends to Maureen is not modified and he wants her to be sure it came only from him, he can digitally sign the message. This means that a one-way hashing function would be run on the message, and then Kevin would encrypt that hash value with his private key.

When Maureen receives the message, she will perform the hashing function on the message and come up with her own hash value. Then she will decrypt the sent hash value (digital signature) with Kevin’s public key. She then compares the two values, and if they are the same, she can be sure the message was not altered during transmission. She is also sure the message came from Kevin because ...

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