Cryptography Tutorials - Herong's Tutorial Examples ∟Introduction to DES Algorithm ∟DES Key Schedule (Round Keys Generation) Algorithm This section describes DES (Data Encryption Standard) algorithm - A 16-round Feistel cipher with block size of 64 bits. Key schedule algorithm: Input: K: 64-bit key PC1: Permuted choice 1 PC2: Permuted choice 2 r1, r2, ..., r16: left shifts (rotations) Output: k1, k2, ..., k16: 16 48-bit round keys Algorithm: K' = PC1(K), applying permuted choice 1 and returning 56 bits (C0, D0) = K', dividing K' into two 28-bit parts (C1, D1) = (r1(C0), r1(D0)), shifting to the left k1 = PC2(C1,D1), applying permuted choice 2 and returning 48 bits (C2, D2) = (r2(C1), r2(D1)), shifting to the left k2 = PC2(C2,D2), applying permuted choice 2 and returning 48 bits ...... k16 = PC2(C16,D16)DES key schedule supporting tables: Permuted Choice 1 - PC1: 57 49 41 33 25 17 9 1 58 50 42 34 26 18 10 2 59 51 43 35 27 19 11 3 60 52 44 36 63 55 47 39 31 23 15 7 62 54 46 38 30 22 14 6 61 53 45 37 29 21 13 5 28 20 12 4Permuted Choice 2 - PC2: 14 17 11 24 1 5 3 28 15 6 21 10 23 19 12 4 26 8 16 7 27 20 13 2 41 52 31 37 47 55 30 40 51 45 33 48 44 49 39 56 34 53 46 42 50 36 29 32Left shifts (number of bits to rotate) - r1, r2, ..., r16: r1 r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12 r13 r14 r15 r16 1 1 2 2 2 2 2 2 1 2 2 2 2 2 2 1Table of Contents About This Book Cryptography Terminology Cryptography Basic Concepts Introduction to AES (Advanced Encryption Standard) ►Introduction to DES Algorithm What Is Block Cipher? DES (Data Encryption Standard) Cipher Algorithm ►DES Key Schedule (Round Keys Generation) Algorithm DES Decryption Algorithm DES Algorithm - Illustrated with Java Programs DES Algorithm Java Implementation DES Algorithm - Java Implementation in JDK JCE DES Encryption Operation Modes DES in Stream Cipher Modes PHP Implementation of DES - mcrypt Blowfish - 8-Byte Block Cipher Secret Key Generation and Management Cipher - Secret Key Encryption and Decryption Introduction of RSA Algorithm RSA Implementation using java.math.BigInteger Class Introduction of DSA (Digital Signature Algorithm) Java Default Implementation of DSA Private key and Public Key Pair Generation PKCS#8/X.509 Private/Public Encoding Standards Cipher - Public Key Encryption and Decryption MD5 Mesasge Digest Algorithm SHA1 Mesasge Digest Algorithm OpenSSL Introduction and Installation OpenSSL Generating and Managing RSA Keys OpenSSL Managing Certificates OpenSSL Generating and Signing CSR OpenSSL Validating Certificate Path "keytool" and "keystore" from JDK "OpenSSL" Signing CSR Generated by "keytool" Migrating Keys from "keystore" to "OpenSSL" Key Files Certificate X.509 Standard and DER/PEM Formats Migrating Keys from "OpenSSL" Key Files to "keystore" Using Certificates in IE Using Certificates in Google Chrome Using Certificates in Firefox Archived Tutorials References Full Version in PDF/EPUB This set of Cryptography Multiple Choice Questions & Answers (MCQs) focuses on “The Data Encryption Standard (DES) and It’s Strength”. 1. DES follows Answer: c 2. The DES Algorithm Cipher System consists of ____________rounds (iterations) each with a round key Answer: d 3. The DES algorithm has a key length of Answer: c 4. In the DES algorithm, although the key size is 64 bits only 48bits are used for the encryption procedure, the rest are parity bits. Answer: b 5. In the DES algorithm the round key is __________ bit and the Round Input is ____________bits. Answer: a 6. In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via ____________ Answer: a 7. The Initial Permutation table/matrix is of size Answer: c 8. The number of unique substitution boxes in DES after the 48 bit XOR operation are Answer: a 9. In the DES algorithm the 64 bit key input is shortened to 56 bits by ignoring every 4th bit. Answer: b Sanfoundry Global Education & Learning Series – Cryptography and Network Security. To practice all areas of Cryptography and Network Security, here is complete set of 1000+ Multiple Choice Questions and Answers.  Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn. Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses. How many bits is a DES round key?However, every 8th key bit is ignored in the DES algorithm, so that the effective key size is 56 bits. But, in any case, 64 bits (16 hexadecimal digits) is the round number upon which DES is organized.
How many round keys are generated by DES?Data Encryption Standard. |
