1. Tony Nguyen Symmetric key encryption performance analysis

2. Symmetric vs. Asymmetric • Symmetric encryption: known as secret key cryptography, which requires the sender and receiver of a message to share the use of a single, common key for encryption and decryption. • Asymmetric encryption: known as public key cryptography, which employs two keys: public key to encrypt message and private key to decrypt them. • Advantages: Symmetric encryption is much faster than asymmetric and required less computation power. • Disadvantages: Private key must be shared among parties involved encryption and decryption. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 1/15

3. Symmetric vs. Asymmetric [2] [KetuFile White Papers] 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 2/15

4. Data Encryption Standard (DES) • Invented in 1976 by IBM based on the Lucifer Algorithm. • Original key size was 128 bits but reduced to 56 bits. (NSA controversy) • Encrypts and decrypts data in 64-bit blocks. • Total keys = 2 ^ 56 = 72,057,594,037,927,936. • Broken by brute force attack using DES Crackers within 22 hours. (245 billion keys/sec) 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 3/15

5. Key Generation Permutation • Initial input key for DES is 64 bits long. • Right most bit is parity big and it is being ignored. • Pass through permutation and produced 56 bits key length. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 4/15

6. Generate sub-keys • Use 56-bit key to generate 16 48-bit sub-keys. • Use 16 48-bit sub-keys to encrypt and decrypt 16 rounds for DES. • Current 56-bit keys split into two 28-bit blocks left and right. • Rotate left and right by the number of bits specified in the table. • Join left and right to get the new K. • Apply Permuted Choice 2 to get the final sub-key. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 5/15

7. Plaintext Preparation • Passing plain text through a permutation called the Initial Permutation. • Then pass it through the Final Permutation or Inverse Initial Permutation. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 6/15

8. DES Core Function • 64-bit block of input data split into two halves, L and R. • Data from R[I-1] is XOR with K[I] (16 sub-keys) and stored in the buffer. • Data is split into 8 segments of 6 bits each and submit to S-boxes. • Results passed into the Permutation. • Data is now XOR with L[I-1] and moved into R[I]. R[I-1] is moved into L[I]. • Repeat the core function until we have completed 16 rounds. • When L[16] and R[16] obtained, they join back in the same fashion as they were split apart. • Apply the Inverse Permutation to the pre-output which results in encrypted text. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 7/15

9. Modes of Operation • Electronic Code Book (ECB): Data is divided into 64-bit blocks and encrypted one at a time. It is fastest and easy to implement but cannot detect re-order contents. • Cipher Block Chaining (CBC): Each block of encrypted cipher text is XOR with the next plaintext block. All blocks dependent on previous blocks. More secure than ECB because the extra XOR step. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 8/15

10. Triple DES • Similar to DES. • Invented by IBM in 1978. • Encrypts and decrypts data in 64-bit blocks. • Key size: 192 bits. • Modes of Operation: ECB and CBC. • Very secure if implemented correctly. • Safe to use until 2035. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 9/15

11. Blowfish • Invented in 1993 by Bruce Schneier. • 64-bit block cipher. • Key length: 32 to 448 bits. • No effective cryptanalysis on the full-round version of Blowfish as of 2008. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 10/15

12. Advanced Encryption Standard (AES) • Invented by Vincent Rijmen and Joan Daemen in 1998. • Encrypts and decrypts data in 128-bit blocks. • Key size: 128, 192 or 256 bits. • Structure: substitution-permutation network. • Most popular and secure for symmetric key cryptography. • No effective cryptanalysis of it has been found to date. 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 11/15

13. Milliseconds 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 12/15

14. Milliseconds 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 13/15

15. Demo • Java GUI application. • Java Security Library. • Maximum file size: 50 MB • File restriction: Jar file • Algorithms: DES, 3DES, Blowfish, AES 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 14/15

16. References • DES Encryption, http://www.tropsoft.com/strongenc/des.htm • Triple Data Encryption Standard (TDES), http://www.vocal.com/tdes.html • The Blowfish Encryption Algorithm, http://www.schneier.com/blowfish.html • The Advanced Encryption Standard (Rijndael), http://www.quadibloc.com/crypto/co040401.htm • The Enduring Value of Symmetric Encryption, http://etoken.mikrobeta.com.tr/PDF/WP-SymmetricEncryption.pdf • KetuFile White Papers, http://www.ketufile.com/Symmetric_vs_Asymmetric_Encryption.pdf 12/10/2008 Symmetric Key Encryption Performance Analysis CS591 Page 15/15