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Security Introduction to Data Security Solutions Communications

Loris Guerra
Loris Guerra
17,536 Points

Confusion about Shared Secret Key

In this example, if Bob and Alice agree together on a Shared-Secret-Key that they use to encrypt messages, (and this Shared-Key is also switched-changed often), how could they still decrypt all the messages using their own private key?

2 Answers

Steven Parker
Steven Parker
221,963 Points

They wouldn't need a private key if they do symmetric encryption.

The shared key would be the only key needed to encrypt and decrypt the messages. Changing it often prevents someone who manages to acquire it from reading their entire message history, or messages they generate in the future after the next change.

If they were using private keys, they would not use a shared key. Each of them would have a unique private key and a public key (4 keys total).

Patrick Palmowski
Patrick Palmowski
4,042 Points

Now I´m confused, do they use a public key now? Because why would they use a shared private key, it just has the characteristics like a public key. Am I so wrong?

Steven Parker
Steven Parker
221,963 Points

A "private" key would not be shared. And private keys (along with pubic keys) are used in a different kind of encryption.

In the kind of encryption that this question was asking about, the shared secret key is the only key used.