Symmetrical encryption

This is a method known for thousands of years and is based on the fact that the sender and the recipient both have access to a message by knowing a secret shared key. This key can take on a wide variety of forms: The Romans used a stick of a certain diameter for encryption and decryption.

Today's digital communications rely in the main upon a password as the key. Using this password and an encryption algorithm, the data from the sender are changed. The recipient uses the same key and the fitting encryption algorithm so that the data are legible again. Other persons who do not know the key cannot read the data. A common symmetrical method of encryption is 3DES, for example.





Example:

  1. Alice wishes to send a confidential message to Bob. To this end, she encrypts the message with a secret key and a suitable method, e.g. 3DES. She sends the encrypted message to Bob informing him of the encryption method she used.
  2. Bob has the same key as Alice. Since he knows the encryption method that was used, he can decrypt the message and transform it back into cleartext.

Symmetrical encryption is simple and efficient but has two serious disadvantages:

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