Public-Key Cryptology

An Asymmetrical Approach to Encryption

Overview

• Symmetric Cryptology

• Asymmetric Cryptology• Digital Signature

• Public-Key Utilization

• Output of Typical Java Public-Key Encryption Program• Security Discussion

• Q&A

Symmetric Cryptology

• A (unlocked); B(locked)

• A > B (Locking)

• B > A (Unlocking)

Digital Signature

• A, C (Locked); B (Unlocked)

• A > B > C (Private Key)

• C > B > A (Public Key)

Public-Key Utilization

• Reverse of the digital signature method.

• Public key is used first.

• C > B > A (Public Key)

• A > B > C (Private Key)

• Only the person with the private key can access this message.

Java Program Output

• Keys are just very large integers. (BigIntegers)

• This program utilizes the BigInteger class to make keys.

• Output on next slide.

Output

Plaintext: Yellow and Black Border Collies

Ciphertext:9836616982166653482645006372197464130512685598624446688038209259229811715639585877358783636599416258581268159312178855357078473798790637852219720576465697138560292629947891863632967992128391246425929118796048947648339967197944410272433013222944564883825985745203197057480292429589977355320433224626523346630

Plaintext: Yellow and Black Border Collies

Brute Force

• The only guaranteed method for decrypting an encrypted message without a key is through a brute-force method.

• Test every integer until it matches the correct key.

• Use the found BigInteger to decrypt the message.

• This can take a considerable amount of time.

• Thus, public-key encryption is extremely secure.

References

• http://en.wikipedia.org/wiki/Public-key_cryptography

• https://www.comodo.com/resources/small-business/digital-certificates2.php

• http://www.webopedia.com/TERM/P/public_key_cryptography.html

• http://computer.howstuffworks.com/encryption3.htm

Image References

• http://1.bp.blogspot.com/-X2116y6RLGI/TnnGt5QXjUI/AAAAAAAAAWU/wD-erptNO5E/s1600/symmetric+encryption.gif

• http://atozdigitalstore.com/images/IC42508.gif

• https://i-msdn.sec.s-msft.com/dynimg/IC21919.gif