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Java Servlet Programming by Jason Hunter

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Digital Certificates

Real applications require a higher level of security than basic and digest authentication provide. They also need guaranteed confidentiality and integrity, as well as more reliable authentication. Digital certificate technology provides this.

The key concept is public key cryptography. In a public key cryptographic system, each participant has two keys that are used to encrypt or decrypt information. One is the public key, which is distributed freely. The other is a private key, which is kept secret. The keys are related, but one can not be derived from the other. To demonstrate, assume Jason wants to send a secret message to Will. He finds Will’s public key and uses it to encrypt the message. When Will gets the message, he uses his private key to decrypt it. Anyone intercepting the message in transit is confronted with indecipherable gibberish.

Public key encryption schemes have been around for several years and are quite well developed. Most are based on the patented RSA algorithm developed by Ron Rivest, Adi Shamir, and Leonard Adelman. RSA uses very large prime numbers to generate a pair of asymmetric keys (i.e., each key can decode messages encoded with the other). Individual keys come in varying lengths, usually expressed in terms of the number of bits that make up the key. 1024- or 2048-bit keys are adequate for secure RSA communications.

Because keys are so large, it is not practical for a user to type one into her web brower for each request. Instead, ...

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