2.1 Key Generation The keys k 1 and k 2 are derived using the functions P10, Shift, and P8. P10 is de ned as follows: P10 3 5 2 7 4 10 1 9 8 6 P8 is de ned to be as. P10 and P8 are such functions, which mimic PC1 and PC2 in DES. They are part of the definition of S-DES. P10 is an entirely arbitrary permutation of 10 bits. P8 is a selection of 8 bits out of 10. Save Save G-SDES For Later. Presented by G Madhukar Rao Key Generation S-DES Operation Fixed values for S-DES Operation Key. Conversion of P10 into P8. Subkey generation. First, produce two subkeys K 1 and K 2: K 1 = P8(LS(P10(key))) K 2 = P8(LS(LS(P10(key)))) where P10(k 1 k 2 k 3 k 4 k 5 k 6 k 7 k 8 k 9 k 10) = k 3 k 5 k 2 k 7 k 4 k 10 k 1 k 9 k 8 k 6. It's convenient to write such bit substitution operators in this notation.
- Sdes P10 And P8 Key Generation 8gb
- Sdes P10 And P8 Key Generation 128gb
- Sdes P10 And P8 Key Generation User
- Sdes P10 And P8 Key Generation 10.2
- Sdes P10 And P8 Key Generation Model
The S-DES encryption algorithm takes an 8-bit block of plaintext and a 10-bit key as input and produces an 8-bit block of ciphertext as output. The S-DES decryption algorithm takes an 8-bit block of ciphertext and the same 10-bit key used to produce that ciphertext as input and produces the original 8-bit block of plaintext.
S-DES key generation. Figure 8.2 shows the key generation algorithm in S-DES. A 10-bit shared secret key is input to P10, of which the output is split into two 5-bit halves. A left shift is performed on each half. The two 5-bit halves are input to P8, and the output of P8 becomes round key K 1.
The encryption algorithm involves five functions: an initial permutation (IP); a complex function labeled fK, which involves both permutation and substitution operations and depends on a key input; a simple permutation function that switches (SW) the two halves of the data; the function fK again; and finally a permutation function that is the inverse of the initial permutation (IP–1).
We can concisely express the encryption algorithm as a composition1 of functions. Download battlefield 2 free mac.
This is a program for Encryption and Decryption with Modifies & Simplified DES. This Algo takes 8-bits of plaintext at a time and produces 8-bits of ciphertext. It uses 10-bits of key for Encryption and Decryption.
Global Variables
Original S-Box
Modified S-Box
Selection of Function for Original and Modified S-Box
We now describe the mapping F. The input is a 4-bit number (n1n2n3n4). The first operation is an expansion/permutation operation:
E/P = (4, 1, 2, 3, 2, 3, 4, 1)
Sdes P10 And P8 Key Generation 8gb
The first 4 bits (first row of the preceding matrix) are fed into the S-box S0 to produce a 2- bit output, and the remaining 4 bits (second row) are fed into S1 to produce another 2-bit output.
Sdes P10 And P8 Key Generation 128gb
These two boxes are defined as follows:
The S-boxes operate as follows. The first and fourth input bits are treated as a 2-bit number that specify a row of the S-box, and the second and third input bits specify a column of the Sbox. The entry in that row and column, in base 2, is the 2-bit output.
Next, the 4 bits produced by S0 and S1 undergo a further permutation as follows:
P = (4, 2, 4, 3, 1)
The output of P4 is the output of the function F.
Shifting of Keys
Key Generator
A 10-bit key shared between sender and receiver. From this key, two 8-bit subkeys are produced for use in particular stages of the encryption and decryption algorithm.
First, permute the key in the following fashion. Let the 10-bit key be designated as (k1, k2, k3, k4, k5, k6, k7, k8, k9, k10). Then the permutation P10 is defined as:
P10 (k1, k2, k3, k4, k5, k6, k7, k8, k9, k10) = (k3, k5, k2, k7, k4, k10, k1, k9, k8, k6)
P10 = (3, 5, 2, 7, 4, 10, 1, 9, 8, 6)
Next we apply P8, which picks out and permutes 8 of the 10 bits according to the following rule:
P8 = (6, 3, 7, 4, 8, 5, 10, 9)
Sdes P10 And P8 Key Generation User
We then go back to the pair of 5-bit strings produced by the two LS-1 functions and perform a circular left shift of 2 bit positions on each string.
Finally, P8 is applied again to produce K2.
Encryption and Decryption
The input to the algorithm is an 8-bit block of plaintext, which we first permute using the IP function:
IP = (2, 6, 3, 1, 4, 8, 5, 7)
This retains all 8 bits of the plaintext but mixes them up. At the end of the algorithm, the inverse permutation is used:
IP–1 = (4, 1, 3, 5, 7, 2, 8, 6)
The Switch Function
Sdes P10 And P8 Key Generation 10.2
The function fK only alters the leftmost 4 bits of the input. The switch function (SW) interchanges the left and right 4 bits so that the second instance of fK operates on a different 4 bits. In this second instance, the E/P, S0, S1, and P4 functions are the same. The key input is K2.