RSA Analysis
...ts the plaintext from the integer representative m. (see figure 2.1) Figure2.1 Asymmetric Encryption 3. Advantages Compared with other encryption algorithms, RSA has the following advantages: l It can be used for both encryption and authentication l It used more than any other public-key cryptosystem and has more empirical evidence of its security. l More convenience and security, it never needs to be transmitted or revealed to anyone. l RSA can provide digital signatures that cannot be repudiated. 4. The complexity of RSA The main complexity of RSA is the computational complexity. In RSA, the size of the modulus determines how secure an actual use is. Long key length is safer than the short key length, it’s difficult to attack but the cost is very expensive. For example, a 256 bit modulus is easily factored by ordinary people, 384 bit keys can be broken by university research groups or companies, 1024-bit keys should be safe for the immediate future (excluding any major algorithmic advances) and keys of 2048 bits are considered by many to be secure for decades. (http://www.eco.utexas.edu/faculty/Norman/BUS.FOR/course.mat/SSim/key.html) 5. Terms of RSA Some technical terms should be understood when we should be familiar with RSA algorithm. PGD (Pretty Good Privacy) is a personal encryption system for email based on public key technology. Public key is a value provided by some designed authority as an encryption key that combined with a private key derived from the public key, can be used to effectively encrypt messages and digital signatures. Private key or secret key is an encryption /decryption key known only to the party or parties that exchange secret messages. A prime number is a whole number greater than 1. A digital certificate is an electronic “credit card” that establishes your credentials when doing business or other transactions on the web. SSL: Secure Socket Layer protocol for sending encrypted messages on the Internet and Web. 6. Limitation and disadvantages Despite the advantages, RSA encryption is limited by two major physical constraints, chip area and power dissipation. Being regarded as secure is based on number theoretic techniques that involve multiplication of large integers. Microprocessors are fast enough to carry out the necessary computations, but still conventional cryptosystems are usually 10 to 1000 times faster. Therefore encryption of message is invariably done using conventional cryptosystems. So it is used only for the special tasks where their unique capabilities are needed. Another limitation is many of its capabilities can be obtained from conventional cryptosystems. 7. Mathematical calculation of complexity The computa...