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Encryption - Symmetric Cryptography

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Private Key
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Alice and Bob share a key K the adversary does not know
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Alice and Bob agree on cryptosystem and key
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Bob encrypts plaintext using key, sends ciphertext to Alice
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Alice decrypts ciphertext with same key and reads the message
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Advantage: fast
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Disadvantage: keys must be distributed secretly
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Disadvantage: if key is compromised, all is lost
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Disadvantage: number of needed keys is n2


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