Hybrid systems use public-key cryptography to exchange secret keys, which are then used in a symmetric-key cryptography systems.

Just as with other components of a cryptography system, a software random number generator should be designed to resist certain attacks.

The goal in finding these "hard" instances is for their use in public key cryptography systems, such as the Merkle-Hellman knapsack cryptosystem.

The review, which will take three to four months, will begin within weeks, and will consider both the domestic use and export of advanced cryptography systems.

The use of strong cryptography systems on "bulk" messaging remains tightly restricted by the Government.

Mathematical problems are used to construct a cryptography system.

However, for many kinds of simple communication like e-mail, cryptography systems have proved too daunting to most users and as a result are largely not utilized.

Cryptovirology: a software scam in which a public key cryptography system crafts fake keys which encrypt the user's data, but cannot decrypt them unless the user pays for the real key.

But at a briefing held in Washington last month after the announcement of the Clipper program, Government officials said they had no plans to outlaw competing cryptography systems.

However, what specifically has been done to reinforce the cryptography system and to invest in European technology which is our best defence against this threat?