05 - Symmetric and asymmetric encryption

 1. Encryption is a technique used to protect data by making it …………..





 2. Special algorithms called …………are used to convert the data, which is plain text, to ………..text.

  passwords / password

  eyns / eyn

  ciphers / cipher

  unstarred / starred

 3. The plain text is the original data, whereas cipher text is the original data that has been transformed into an unreadable form which is not possible to ………..

  understand without the use of a key

  comprehend without a human

  mix up unless it is going through a cable


 4. Keys are used to …………messages into their original form.
Note: messages are encrypted into cipher text





 5. Symmetric encryption uses the same key for encryption and decryption where as asymmetric encyrption uses…..

  different keys for encryption and decryption

  similar keys for both

  only plain text without the need for keys

  no keys at all

 6. In public key cryptrography, each party using a public/private key encryption scheme has ………….

  two keys, both only known to them and highly confidential.

  two keys, both freely available to the public

  two keys: a private key known only to them and a public freely available key

  a single key, known only to them.

 7. Public and private keys are related to each other - the private key can decode messages encoded by the public key and ….

  the public key can only decode messages that have numbers

  the public key can decode messages encrypted with the private key

  the public key cannot decode messages in order to keep the system secure

  None of the above

 8. The public key can be used to decode messages encoded by itself and the same goes for the private key.



 9. To send an encrypted message to another party, the transmitter will encode the message using the …………………

  public key of the sender

  public key of the receiver

  private key of the sender

  None of the above

 10. Any receiver (not just the correct receiver) has the private key to decode the message and so anyone can decode it.



 11. The 'symmetry' is caused by the fact that the messages encrypted by the public key can only be decrypted using the corresponding private key and …..

  None of the above

  the private key is the same (in binary sequences) as the text itself

  all other messages encrypted using the private key cannot be decrypted

  messages encrypted using the private key can only be decrypted using the public key

 12. Symmetry with public and private keys (encryption and decryption) is what allows for digital signatures.



 13. Symmetric encryption is when the key used to secure a message is used to both encrypt and decrypt a message.



 14. A widely used symmetric encryption key used in the 1990s was the DES (Data encryption standard). In 1998 a powerful machine cracked the key in just three days!
Note: This symmetric key had a 52 bit-secret key which they once thought was highly secure



 15. ………………………..are often found in commercial sectors of the business world as they offer the highest forms of protection.

  key passwords (numerical)

  biometric keys

  asymmetric keys

  symmetric keys

 16. The features/advantages of assymetric key encryption include:
Note: By seperating the keys and making them different, it allows you to control who has the right to read encrypted data.

  The sender doesn't need to to decrypt the data once they've sent it.

  All of the above

  By seperating the keys, people can only send data.

  Only certain people would be able to read the encrypted data.

 17. With ………………….encryption it is possible to see how certain characters are affected and decrypt the message to see the plain text.





 18. Without the …………….it becomes increasibly impossible to retrieve the plain text from the cipher text (in assymetric encryption).

  private key

  public key

  None of the above

  symmetric key

 19. Some 'ransomware' will infect a computer with a virus, encrypt the data on a hard drive with a key, and the user would have to pay to have it 'unlocked'.



 20. Generlally speaking, symmetric encryption is far more secure and reliable than asymmetric encryption.