![]() ![]() ![]() Increase the number of users to 2000, and we’re looking at 2 million keys in total.Īsymmetric encryption overcomes these drawbacks (and a few others), as keys can be generated on the fly and the public key can be shared over insecure channels. For a corporation comprised of 1000 people, this amounts to about half a million keys that need to be generated and distributed securely to the individuals. Furthermore, the number of keys can become large fast: if we require each pair of users to have a separate pair of keys, a network with users would need a total of This is known as the key distribution problem. This means that if Alice and Bob want to communicate using private-key encryption, they must find a way to establish the secret key over a secure channel first. In a symmetric system, the same secret key is used for both encryption and decryption.įigure 1: Principle of symmetric-key encryption While many people believe RSA to be the first public-key encryption, British mathematician Clifford Cocks invented an algorithm equivalent to RSA earlier in 1973, but this remained classified until 1997.Īsymmetric (public-key) cryptography relies heavily on number theoretic functions, and it is quite different from symmetric algorithms such as DES or AES. You may read the original RSA paper here. ![]() It was designed in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman (hence the name). RSA is one of the first public-key cryptosystems, whose security relies on the conjectured intractability of the factoring problem. ![]()
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