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Advanced Encryption Standard (AES): Next-Generation Security Solution

Explore the advanced encryption standard (AES) and its significance in information security, including its robustness, implementation requirements, and comparison with other symmetric ciphers like Triple DES, IDEA, Blowfish, and RC5. Learn about AES's selection process, specifications, implementations in various languages, and practical applications.

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Advanced Encryption Standard (AES): Next-Generation Security Solution

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  1. Information Security and Management(Abstract)5. Advanced Encryption Standard6. Contemporary Symmetric Ciphers Chih-Hung Wang Fall 2011

  2. Famous Symmetric Ciphers • AES (Advanced Encryption Standard) • Triple DES • Other symmetric block ciphers (ex. IDEA、Blowfish、RC5、CAST- 128…etc.)

  3. AES • Next generation encryption standard of NIST/FIPS • It will replace the use of DES in the following 30 years • The sensitive information protected by AES cannot be revealed within 100 years • It is selected by the competition from international selection process

  4. Calendar of AES

  5. AES Requirements • Block cipher • 128-bit block • 128/192/256-bit keys • It is equal to Triple DES at least on security and is more efficient • Provide descriptions and analysis • Provide three implementations in two languages (reference and optimized in C，optimized in Java) • IF selected, royalty free world wide

  6. The 15 Submission for AES (1)

  7. The 15 Submission for AES (2)

  8. Final AES Selection • Rijndael • Block cipher with block size 128 bits • Accept 128-, 192-, 256-bit length keys • Easy to implement in H/W

  9. The Implementation of Crypto Algorithms (W32) • http://us.cryptosoft.de/ • Different platforms: win16, win32, linux, OS/2,… • Triple DES, Rijndael, Safer+, Blowfish, Cast-128, … • Old version • Crypto++: a C++ Class Library of Cryptographic Primitives • Version 5.6.1 (2010/8/9) • http://www.cryptopp.com/ • Microsoft CryptoAPI

  10. More AES Information • NIST AES Homepage • http://csrc.nist.gov/encryption/aes/ • Rijndael Specification Those who are interested in the AES specification (i.e., what will be in the standard) should refer to the Draft FIPS for the AES. • Test Values • Supporting Documentation • Rijndael Developers' Contact Information • Rijndael Code: C/C++/Java/Visual Basic • FIPS 197 • http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf • AES proposal • http://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf

  11. Practice • Reading Project • Rijndael Specification : download from http://csrc.nist.gov/encryption/aes/ • Programming/testing Project • Download Rijndael source code (C/C++) from Rijndael homepage or other web sites. • Modify and refine the source code from web sites such that it can be used to encipher and decipher a message. • Write a report that includes the address of web sits, source code and testing results.

  12. Triple DES • Double DES

  13. Triple DES • Double DES: reduction to a single key • It would be possible to find a key K3 such that • With 264 possible inputs, how may different mappings? (264)! > (101020) • It is reasonable to assume that if DES is used twice with different keys, it will produce one of the many mappings that is not defined by a single application of DES.

  14. Meet-in-the-Middle Attack • Works whenever use a cipher twice [DIFF77] • Since X = EK1[P] = DK2[C] • Attack by encrypting P with all keys and store • Then decrypt C with keys and match X value • Can show takes O(256) steps

  15. Triple DES • Triple DES with two keys • C=EK1[DK2[EK1[P]]] • P=DK1[EK2[DK1[C]]]

  16. Triple DES • Standardized in ANSI X9.17 & ISO 8732 • No current known practical attacks • The cost of a brute-force key search on triple DES: 2112 (51033) • Has been adopted by some Internet applications, eg PGP, S/MIME

  17. Known-Plaintext Attack

  18. Other symmetric block ciphers • IDEA • International Data Encryption Algorithm • A symmetric block cipher developed by Xuejia Lai and James Massey of the Swiss Federal Institute of Technology. • One of a number of conventional encryption algorithms that have been proposed in recent years to replace DES. • IDEA is included in PGP. • 128-bit key to encrypt data in blocks of 64 bits

  19. Other symmetric block ciphers • Blowfish • A symmetric block cipher developed by Bruce Schneier. • Characteristics • Fast • Compact: can run less than 5K of memory. • Simple • Variably secure: the key length is variable and can be as long as 448 bits. This allows a tradeoff between higher speed and higher security. • 64-bits block cipher

  20. Other symmetric block ciphers • RC5 • A symmetric encryption algorithm developed by Ron Rivest. • Adaptable to processors of different word lengths. • Variable number of rounds. • Variable-length key • Low memory requirement • Suitable for smart cards

  21. Comparison

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