ccna at aptech

ccna at aptech.Use a secure channel to exchange DES keys between the sender and the receiver.Consider using DES in CBC mode. o Using CBC, each 64-bit block is encrypted in dependence on the previous block. CBC is the most widely used DES mode. Test a key before using it to see if it is a weak key. DES has 4 weak keys and 12 semi-weak keys. Since there are 2% of possible DES keys, the probability of selecting one of these keys is very low. However, testing the key does not have a significant effect on the encryption time and is therefore recommended.DES is considered a good protocol for protecting data due to the short key length and therefore only for a very short period of time °3DES is a better choice for protecting data. The algorithm of 3DES is considered to be very trustworthy and has higher security strength.7.3.3 3DES7.3.3.1 Using 3DES to enhance DESWith advances in computer processing power, the initial 56-bit DES key has become too short to make breaking DES difficult for an attacker with a full budget in hacking techniques. One way to increase the effective key length of DES without changing the algorithm with good analysis is to apply the same algorithm multiple times in a row, but using a different key each time.The technique of applying DES three times in a row to a block of plaintext is known as 3DESo today, brute force cracking of 3DES is considered infeasible because the underlying algorithm has been tested in this field for over 35 years and is considered highly trustworthy. The CiscoIPSec implementation uses the CBC model of DES and 3DES-7.3.3.2 3DES Operation 3DES uses an encryption called 3DESEncryption . Decryption . Encryption (3DES-Encrypt-Decrypt-Encrypt,3DES-EDE) method to encrypt plaintext. First, the message is encrypted using a first 56-bit key (K1). Next, the data is decrypted using a second 56-bit key (K2). Finally, the data is encrypted again, using a third 56-bit key (K3). 3DES-EDE is far more efficient at improving security than simply encrypting the data three times using three different keys. Encrypting data three times in a row using different 56-bit keys is equivalent to a 58-bit key length. Whereas the 3DES-EDE process provides an encryption with an effective key length7.3 Confidentiality 203