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Symmetric Key in Use

CISSP, GIAC GSEC, Security+ Review

For some unknown reason, "Alice" and "Bob" are always used in examples when crypto is discussed.

We'll be politically correct and use the following scenario.

Alice is an old battle axe and former Playboy Bunny from the previous millenium, and she is having an affair with her secretary Bob, who is less than half her age. This is not fundamentally a problem, except that Alice's boyfriend, who is a billionaire twice her age, is very jealous. Despite his borderline senility, Alice insists on keeping their affair confidential, and they use secret key encryption to keep their electronic communications confidential.

Alice, wearing a hot red dress, sends Bob a steaming message, simplified to "Hi Bob, Alice" as this is a family Web destination. She encrypts it using their shared secret key.

Billionaire boyfriend, shown in grey on the bottom of the diagram, sees the message,  but it's encrypted and he doesn't understand it. Fortunately he doesn't become suspicious, as one might seeing clearly encrypted or at least nonsensical communications, as he's borderline senile. Even if he wasn't, he couldn't understand the message.

Secretary Bob on the right, wearing the blue Tutu (he's a wannabe ballerina in his spare time), can decrypt his boss and lover's message as he also has the secret key.

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