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Security When the Enemy Knows the System

Security When the Enemy Knows the System

Cryptography works with the assumption that adversaries know the implementation. We'll study this concept more in this lesson.

So if the entire implementation of our cryptosystems is known to the adversary, how can we be secure? The adversary can just run our code after all.

The key is key

The key is key. Encryption algorithms don’t just take plain text as input, they take a key as well. A well-written encryption algorithm will produce wildly different outputs when encrypting a given plaintext with keys that differ only slightly. The key is the only part that needs to be kept secret. Rather than keeping an entire algorithm secret, we just need to keep our key secret.

An encryption algorithm should be so ...

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