13-12-2012, 06:24 PM
Diffie-Hellman-RSA
Diffie-Hellman-RSA.ppt (Size: 110.5 KB / Downloads: 37)
Diffie-Hellman Algorithm
Whitfield Diffie and Martin Hellman, both of Stanford University
In 1976 they discovered the public key method
Diffie had the question of an alternative to symmetric key while working with the Multics group at MIT. Multics was a classified project and trusting every one in the group became essential before sharing any findings.
D-H Advantages
Any user can choose a random x and publish gx in a public database such as a phone book
Phone book must be maintained by a TTP
Other users can look up the database and get the public key for the individual and use it to encrypt the message
Ideal for use with emails
RSA Algorithm
Rivest-Shamir-Adleman, all at MIT in 1978
D-H method uses a one way function
RSA method uses a trapdoor one way function
Given n and e, it is easy to calculate
me (mod n).
If factors of n are known then the reverse calculation is easy. The trapdoor is the difficulty of knowing the factors of n.
RSA Benefits
RSA can be used both for encryption as well as for digital signatures
Trapdoor in RSA is in knowing value of n but not knowing the primes that are factors of n