O'Reilly logo

Computer Security and Cryptography by Alan G. Konheim

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

10.4 PUBLIC-KEY CRYPTOSYSTEMS: EASY AND HARD COMPUTATIONAL PROBLEMS

Diffie and Hellman proposed a new type of cryptosystem that would alleviate but not eliminate the problem of key distribution and also provide a mechanism for digital signatures. The characteristic property of conventional cryptosystems image = {Tk : k image} is that Tk determines the inverse transformation image. Normally, the key k determines a second key k−1 so that image. Diffie and Hellman proposed (public-key) cryptosystems that used two keys: a public key PuK for encipherment and a private key PrK for decipherment.

Encipher : xy = EpuK{x}

Decipher : yx = EPrK{x}.

In addition to the usual properties required of a strong cryptosystem, it was crucial that the computation of PrK with knowledge of PuK would be infeasible. User_ID[A] would publish the public key PuK(ID[A]) and thereby enable every user to encipher information intended only for User_ID[A]. Knowledge of PrK(ID[A]), known only by User_ID[A], would permit User_ID[A] to decipher such messages. How can such pairs (PuK(ID[A]), (PrK(ID[A])) be found?

Diffie and Hellman argued ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required