Cryptography Hands-On Learning Lab at University of South Alabama

Dive into the world of cryptography with the Cryptography Hands-On Learning Lab Activity (HOLLA) at the University of South Alabama's School of Computing. Explore fundamental encryption principles, shift ciphers like Julius Caesar's, symmetric encryption, and cryptanalysis techniques. Learn to encrypt, decrypt, and analyze secret messages, enhancing your understanding of secure communications. Join this educational initiative to develop your skills in information security and live out the thrill of breaking codes.

• Cryptography
• University of South Alabama
• Encryption
• Cryptanalysis
• Information Security

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1. Cryptography Hands on Learning Lab Activity (HOLLA) K-12 Partner School Initiative School of Computing University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

2. Educational Outcomes At the end of this block, the student will be able to: Explain how a shift cipher works Encrypt a message Decrypt a message Perform cryptanalysis on a secret message University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

3. Part 1: Cryptographic Fundamentals Cryptography Study of encryption principles/methods From Greek Hidden writing/study Uses: Computer passwords, credit card transactions, banking transactions, etc. Ancient Greek scytale University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

4. Symmetric Encryption ciphertext plaintext plaintext Shared Key University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

5. Shift Cipher Dates back to Julius Caesar Shift each letter by 3 spaces Can define transformation as: Mathematically give each letter a number Shift Cipher Formula (k =3 (c) for Caesar s) c = E(k, p) = (p + k) mod (26) p = D(k, c) = (c k) mod (26) University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

6. Examples Example 1: Encryption i have a secret Example 2: Decryption WKH GRJ DWH PB KRPHZRUN Much easier to do in a Tool University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

7. Part 2: Cryptanalysis Cryptanalysis Code breaking Study of principles/ methods of deciphering ciphertext without knowing key (the shift amount) How to break Brute Force Letter frequency analysis University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

8. Brute Force Brute Force is an exhaustive search Given ciphertext, just try all shifts of letters 26 possibilities Must recognize when plaintext found Example 3: DTZ RZXY UNHP YMJ HTWWJHY XMNKY FRTZSY Example 4: (you try) TIJGU DPVME CF GPSXBSE PS CBDLXBSE University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

9. Letter Frequency Analysis E most common, then T Assumes that you have a large message University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

10. JCryp Tool Frequency Analysis University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

11. Frequency Analysis Tool Example 5 YXURCRLRJWB JWM VRURCJAH BCAJCNPRBCB QJEN DBNM BRVYUN-BDKBCRCDCRXW LRYQNAB CX NWLXMN CQNRA BNLANC MXLDVNWCB OXA CQXDBJWMB XO HNJAB - NENW KJLT CX CQN CRVN XO SDURDB LJNBJA! CQN YAXLNBB RB BRVYUN: LQJWPN NJLQ UNCCNA RW HXDA MXLDVNWC CX JWXCQNA UNCCNA RW CQN JUYQJKNC, BX CQJC HXDA WNF MXLDVNWC RB LXVYUNCNUH RUUNPRKUN. University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

12. Frequency Analysis Exercise Exercise 1 JYFWAVNYHWOF WYPVY AV AOL TVKLYU HNL DHZ LMMLJAPCLSF ZFUVUFTVBZ DPAO LUJYFWAPVU, AOL JVUCLYZPVU VM PUMVYTHAPVU MYVT H YLHKHISL ZAHAL AV HWWHYLUA UVUZLUZL. AOL VYPNPUHAVY VM HU LUJYFWALK TLZZHNL ZOHYLK AOL KLJVKPUN ALJOUPXBL ULLKLK AV YLJVCLY AOL VYPNPUHS PUMVYTHAPVU VUSF DPAO PUALUKLK YLJPWPLUAZ, AOLYLIF WYLJSBKPUN BUDHUALK WLYZVUZ AV KV AOL ZHTL. ZPUJL DVYSK DHY P HUK AOL HKCLUA VM AOL JVTWBALY, AOL TLAOVKZ BZLK AV JHYYF VBA JYFWAVSVNF OHCL ILJVTL PUJYLHZPUNSF JVTWSLE HUK PAZ HWWSPJHAPVU TVYL DPKLZWYLHK. Exercise 2 XQTFIEX HY IHHK WBLMKBUNMBHG YKHF LFTEE LTFIEX University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing

13. Wrap Up What we learned Cryptography The shift cipher How to encrypt and decrypt a message Cryptanalysis How to decrypt a message by breaking the key Other Tools Caesar Cipher tools available on iPAD/iPOD Droid Online: http://www.cryptool-online.org/ University of South Alabama CFITS (Center for Forensics, Information Technology, and Security) School of Computing