There are no efficient algorithms for "breaking" RSA once its key is 2,048 bits long. However, American mathematician Peter Shor (born 1959) devised an efficient probabilistic algorithm capable of doing so, but only on a type of computer that does not yet exist: a "quantum computer." Such a machine relies on qubits ("quantum bits"): through the superposition of two quantum states, it can represent 2*n* states simultaneously at the start of a computation, where n is the number of qubits. In theory, computations on qubits are equivalent to parallel computations—provided the qubits can be kept in this superposition long enough to complete them. The quantum computer should not be confused with quantum cryptography, which can be used to create and transmit random keys. At present, quantum computers are not sufficiently developed to perform computations using more than 50 qubits, and it is unclear whether they ever will be. If quantum computers became a reality, the transfer of symmetric keys would have to be reconsidered; it may be wise to prepare for that possibility.
Quantum computers: a threat to encryption | Tangente
Quantum computers: a threat to security?
Internet communications are currently secured by symmetric encryption systems such as AES, whose keys are transmitted using an asymmetric encryption system such as RSA.
