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ccna at buet.is 168 bits. In some implementations, the keys K1 and K3 are the same, in which case a slightly less secure encryption of 112 bits is obtained. To decrypt the message, the reverse procedure of the 3DES-EDE method is used. First, the ciphertext is decrypted using key K3. Next, the data is encrypted using key K2. Finally, the data is decrypted using the key KI. Although 3DES is very secure, it is very resource intensive. For this reason, the AES encryption algorithm was developed. It proved to be as secure as 3DES - but much faster.7.3.4 Advanced Encryption Standard (AES)7.3.4.1 Origin of AESAfter a few years, it was realized that DES would eventually lose its effectiveness. In 1997, the AES scheme was announced and the public was invited to propose encryption schemes to replace DESo after a five-year standardization process in which 15 designs were demonstrated and evaluated, the National Instituteof StandardsandTechnology (NIST) selected the Rijndael block cipher as the AES algorithm.The Rijndael cipher was developed by Joan Daemen and Vincent Rijmen and has variable block length and key length. Rijndael is an iterative block cipher, which means that the initial input block and the cipher key undergo multiple transformations before producing the output. The algorithm can operate on variable-length blocks using variable-length keys. Blocks of 128, 192 or 256 bits can be encrypted using 128, 192 or 256 bit keys, and all 9 combinations of key and block length are possible.Rijndael's accepted AES implementation contains only a fraction of the capabilities of Rijndael's algorithm. The algorithm itself allows easy extensions to either block length or key length or both in 32-bit integer multiples, and the system has been specifically designed to allow efficient implementation on a wide range of processor hardware and software.The AES algorithm has been intensively analyzed and is currently used worldwide. AES using the Rijndael cipher is the more efficient algorithm, although not to the extent of 3DES in everyday applications. It can be used in high throughput, low latency environments, especially when 3DES cannot meet the throughput or latency requirements. With time and more attacks against it, it is expected that AES will gain more trust.7.3.4.2 AES SummaryAES was chosen to replace DES for several reasons. The key length of AES makes its keys much stronger than DES. AES is faster than 3DES when running on hardware with comparable performance. On similar hardware, AES is more efficient than DES and 3DES, typically 5 times more efficient than DES. AES is better suited for high-throughput, low-latency environments, especially when using pure software encryption.Despite these advantages, AES is still a relatively young algorithm. The golden rule of cryptography is that a mature algorithm is more trustworthy. Therefore, in terms of strength, 3DES is the more trustworthy choice because it has been tested and analyzed for 35 years. The following CiscoVPN devices support cryptographic conversion using AES.