Pattern Recognition and Applications Lab CRYPTOGRAPHY Giorgio Giacinto
[email protected] University of Cagliari, Italy Spring Semester 2019-2020 Department of Electrical and Electronic Engineering Cryptography and Security • Used to hide the content of a message • Goals – Confidentiality – Authenticity – Integrity • The text is modified by an encryption function – An interceptor should not be able to understand all or part of the message content http://pralab.diee.unica.it 2 Encryption/Decryption Process Key Key (Optional) (Optional) Original Plaintext Encryption Ciphertext Decryption Plaintext http://pralab.diee.unica.it 3 Keys and Locks http://pralab.diee.unica.it 4 Keys L F A Y B D E T C A R C S E E T Y H G S O U S U D H R D F C E I D B T E M E P Q X N R C I D S F T U A E T C A U R M F N P E C J N A C R D B E M K C I O P F B E W U X I Y M C R E P F N O G I D C N T M http://pralab.diee.unica.it 5 Keys L F A Y B D E T C A R C S E E T Y H G S O U S U D H R D F C E I D B T E M E P Q X N R C I D S F T U A E T C A U R M F N P E C J N A C R D B E M K C I O P F B E W U X I Y M C R E P F N O G I D C N T M http://pralab.diee.unica.it 6 Steganography - = http://pralab.diee.unica.it https://towardsdatascience.com/steganography-hiding-an-image-inside-another-77ca66b2acb1 7 Definitions • Cryptography algorithm C = E(K,M) A function E with two inputs – a message M – a key K that outputs – the encrypted message C The algorithm is based on a shared secret between the sender and the receiver K The Encryption Key http://pralab.diee.unica.it 8 Symmetric