Cryptology in CSE

1
Cryptology in CSE

• IIS Lab
• Prof. Lee JeonYoung
• Hur Esther

2
Contents

• Introduction of DES
• Pros and Cons of DES
• Conclusion

3
Private Cryptosystem DES

• Encryption Key Decryption Key
• Plaintext Cipher text 64bit
• Key 56 bit
• IP -gt 16 Rounds with 16 Keys -gtIP-1

4
One Round of DES
Ri-1
L i-1
Ki
f

Ri
L i
5
Pros and Cons of DES

• Easy to understand
• Fast to encrypt and to decrypt
• Use same system to encrypt and to decrypt

• Difficult to Distribute Key Securely
• Too small Key Space currently

6
Conclusion

• Famous But Old Cryptosystem DES
• Other Cryptosystem IDEA, AES
• Public Cryptosystem RSA