The key-scheduling algorithm is used to initialize the permutation in the array "S." "keylength" is defined as the number of bytes in the key and can be in the range 1 ≤ keylength ≤ 256, typically between 5 and 16, corresponding to a key length of 40 – 128 bits. First, the array "S" is initialized to the identity permutation. S is then processed for 256 iterations in a similar way to the main PRGA, but also mixes in bytes of the key at the same time.
or as many iterations as are needed, the PRGA modifies the state and outputs a byte of the keystream. In each iteration, the PRGA increments i, looks up the ith element of S, S[i], and adds that to j, exchanges the values of S[i] and S[j], and then uses the sum S[i] + S[j] (modulo 256) as an index to fetch a third element of S, (the keystream value K below) which is XORed with the next byte of the message to produce the next byte of either ciphertext or plaintext. Each element of S is swapped with another element at least once every 256 iterations.
Audio steganography - LSB
STEGANOGRAPHY No one apart from the Art and A form of sender and science of security intendedwriting hidden through recipient, messages obscurity suspects the existence of the message www.company.com
AUDIO TERMS• Sampling is the process in whichthe analogue values are only captured at regulartime intervals.• Quantization converts each input value into one of a discrete value.• Popular sampling rates for audio include 8 kHz, 9.6 kHz, 10kHz, 12 kHz, 16 kHz, 22.05 kHz and 44.1 kHz www.company.com
WHY LSB?Low computational complexityEasier ImplementationVariation in choosing LSB www.company.com
LSB ALGORITHM Step 2 Step 4• Receives the • Check which LSB • Replaces the LSB audio file • Each character to Replace By bit from audio convert it into bit in the message is RC4 Algorithm with LSB bit from pattern. converted into character in the bit pattern. message. Step1 Step 3 www.company.com
RC4 ALGORITHM RC4 The pseudo- The key- random scheduling generation algorithm (KSA) algorithm (PRGA)www.company.com
RC4 ALGORITHM• The key-scheduling algorithm (KSA) • initialize the permutation in the array "S • Array "S" is initialized to the identity permutation • Swap values of S[i] and S[j]. www.company.com
RC4 ALGORITHM• The pseudo-random generation algorithm (PRGA) • Used as many iterations as are needed www.company.com