Exercise 66: Massachusetts Spammers


The cryptographic options available with SLES 9 can be broken into two categories: symmetric and asymmetric. With symmetric encryption, the same key used to encrypt data is also used to decrypt it: The sender and the receiver both need the same key. Cryptographic standards using symmetric encryption include

  • Data Encryption Standard (DES)

  • Advanced Encryption Standard (AES)

  • Blowfish

With asymmetric encryption, two keys not one are used. The keys are mathematical opposites of each and are known as the public key and the private key. Because they are opposites, data encoded with the public key can only be decoded with the private key and data encoded with the private key can only be decoded with the public key. Cryptographic standards using asymmetric encryption include

  • Rivest Shamir Adleman (RSA)

  • Digital Signature Algorithm (DSA)

Digital signatures use asymmetric encryption to create an encrypted hash of the message being sent. The hash is sent to the recipient with the message, and the recipient generates a hash of their own. The public key is used to decrypt the hash sent with the message to see if the two hashes are the same if they are, it can be reasoned that the message is original and was not altered. The only weakness in the system lies in verifying that the public key is legitimate, which is the role that certificate authorities (CAs) fulfill.

Encryption schemes express security in terms of the number of bits used to encode the data. While older encryption schemes rely on 40 to 56 bits to encode data, 128 bits, or more, are more common today.



NovellR Linux Certification Practium Lab Manual
NovellR Linux Certification Practium Lab Manual
ISBN: N/A
EAN: N/A
Year: 2004
Pages: 192

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