How to turn the key to privacy

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The Independent Online
Encryption sounds complicated, but is merely a dressed-up version of the secret codes that cloak-and-dagger types have used since Roman times. Plaintext, or ordinary language, is put into ciphertext, which is any kind of combination of letters and numbers.

Ciphertext can be encoded and decoded with two kinds of "keys": synchronous and asynchronous. With synchronous codes, the same key used to put encode is used to decode. A key is a long string of numbers and it is used by a mathematical algorithm to unlock the code.

Asynchronous codes use public and private keys. The same keys can't be used to lock and unlock a message. Everyone using a particular computer system has their own public and private keys. Public keys could be known by many people. Private keys are known only by the user.