When sending your credit card number through a public medium, such as the Internet, your financial credibility may be compromised if the number is not first encrypted. It is impossible to tell who may be listening in on your connection as you shop for new CDs or books. The RSA encryption method often is used to hide your credit card number from would-be thiefs on the Internet, because it uses a public key to hide your information and a private key to reveal it.. . .
When sending your credit card number through a public medium, such as the Internet, your financial credibility may be compromised if the number is not first encrypted. It is impossible to tell who may be listening in on your connection as you shop for new CDs or books. The RSA encryption method often is used to hide your credit card number from would-be thiefs on the Internet, because it uses a public key to hide your information and a private key to reveal it. This article banishes the mystery surrounding RSA encryption and explains how a realistic implementation of RSA works in the OpenSSL library. The only files you need to concern yourself with appear in the openssl/crypto/bn and openssl/crypto/rsa subdirectories. Feel free to download and take a look at the code to get a feel for it before continuing.

Symmetric vs. Asymmetric Encryption

The best way to understand asymmetric encryption is to think of a box that has two kinds of keys: one key locks it and the other unlocks it. Anybody who has a copy of the locking key (aka public key) can put a secret in the box. Because only you have the unlocking key (aka private key), nobody else can reveal a secret that someone else locked in the box. This is different from symmetric key encryption, in which the same key is used for locking and unlocking.

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