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ccna book buy.Confidentiality ---------- IPSec uses encryption to ensure confidentiality.Integrity - IPSec uses a hashing algorithm (such as MD5 or SHA) to ensure that data reaches its destination unaltered.Authentication -------- IPSec uses Internet Key Exchange (IKE) to authenticate users and devices that can communicate independently. IKE uses several types of authentication, including user names and passwords, one-time passwords, biometrics, pre.sharedkey (PSK), and digital certificates.Secure Key Exchange ----------- IPSec provides a public key exchange method for two peers to establish a pre-shared key using the DH algorithm.8.3.1.2 ConfidentialityConfidentiality is achieved by encrypting traffic as it travels through the VPN. The level of security depends on the key length of the encryption algorithm. If someone tries to break the key through a brute force attack, the number of attempts required is related to the key length. The time to process all possibilities is then related to the computer power of the attacking device. The shorter the key, the more likely it is to be cracked. It takes a relatively sophisticated computer about a year to crack a 64-bit key, and about IO]' years to crack a 128-bit key using the same machine.The following are several encryption algorithms and key lengths used by VPNs.DES - Uses a 56-bit key to ensure high-performance encryption. DES is a symmetric key cryptosystem.3DES - a variant of 56-bit DES °3DES uses three separate 56-bit encryption keys for each 64-bit block to provide much stronger encryption than DES. 3DES is a symmetric key cryptosystem. AES - provides stronger security than DES while being computationally more efficient than 3DES. AES offers three different key lengths: 128-bit, 192-bit, and 256-bit. AES is a symmetric key cryptosystem.