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Because of its ability to communicate with the server, the XMLHttpRequest object (XHR), used in the technology Ajax (an acronym for Asynchronous JavaScript and XML, which should be pronounced "egiacs" although we prefer Italian "aiacs"), has a security lock that prevents you from running applications outside the domain in which it operates. This protection is necessary to prevent JavaScript Injection (techniques of "injection" extremely dangerous code in order to break the system) of various kinds, with the ultimate objective of "break" in the system.
This limit is now taken seriously and you're thinking, somehow, to solve it - directly into the XmlHttpRequest - without compromising security (see also: Third Proposal for cross-site extensions to XMLHttpRequest ).

Whatever the situation today is as follows:

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As3 Crypto Framework 1.1 is a library written in ActionScript 3 that allows you to apply the most common encryption algorithms, such as:

• Public Key Encryption: RSA (encryption partial. only.)
• Secret Key Encryption: AES, DES, 3DES, BlowFish, XTEA, RC4
• Confidentiality Modes: ECB, CBC, CFB, CFB8, OFB, CTR
• Hashing Algorithms: MD5, SHA-1, SHA-224, SHA-256
• Paddings available: PKCS # 5, PKCS # 1
• Other Useful Stuff: HMAC, Random

The library offers a variety of classes in order to apply the encryption algorithms. It is BSD licensed, as part of the source code comes from Java, C and JavaScript. On the site you can find more information, the sources and binaries.

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First of all, as mentioned in the Post encryption system RSA is a public key encryption and takes advantage of the properties of prime numbers. Moreover, the arithmetic used (in the calculations) is not the ordinary, but the so-called finite or artirmetica modular. Let's start right from the latter to proceed step by step in the implementation of RSA encryption.

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