Post-quantum cryptography

Post- quantum cryptography (English post- quantum cryptography, PQC ) denotes a branch of cryptography that deals with cryptographic primitives, which are in contrast to most currently used asymmetric cryptosystems even using quantum computers virtually impossible to decipher. The term post- quantum cryptography was introduced by Daniel J. Bernstein, who was also involved in 2006 in the organization of the first conference PQCrypto on this topic.

Asymmetric encryption

The term was coined because the first asymmetric cryptosystems based on the difficulty of factorization and computing discrete logarithms, two problems which theoretically - to be solved by the Shor algorithm - with a sufficiently powerful quantum computers.

The performance of existing quantum computer is not for such calculations is far from sufficient and a scientific breakthrough or milestone hardly predictable; 2001 IBM was only the number to factor in the layer 15.

Symmetric Encryption

For symmetric encryption algorithms such as AES Quantum computers are a relatively small threat, since the measured in bits of a key security would be reduced by half by the Grover algorithm. The increase in computing power could be counteracted with correspondingly longer keys.

Future

Promising seems to be the development of PQ - secure encryption algorithms based on mathematical lattice, which are for example used in 2016 patented NTRUEncrypt as a basis. Moreover, there is research on the basis of

• Multivariate polynomials, for example, the Unbalanced Oil -and- Vinegar method
• Cryptographic hash functions, such as the Merkle signature method or the Lamport - Diffie one-time signature scheme
• Error-correcting codes, such as the McEliece encryption system.

Another area of ​​research is the adaptation of cryptographic proof techniques of quantum attacker. For example, the security proof of a classical zero-knowledge proof method uses a technique called Rewinding, in which the internal state of the attacker is copied. The state of a quantum attacker, after the no -cloning theorem but not always copied the technique of proof must be adapted accordingly.