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Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks. [1] [2] The best known example of quantum cryptography is quantum key distribution, which offers an information-theoretically secure solution to the key exchange problem.
Post-quantum cryptography (PQC), sometimes referred to as quantum-proof, quantum-safe, or quantum-resistant, is the development of cryptographic algorithms (usually public-key algorithms) that are currently thought to be secure against a cryptanalytic attack by a quantum computer.
A quantum computer is a computer that exploits quantum ... An example and possible application of this is a password cracker that attempts to guess a password.
The major difference of quantum key distribution is the ability to detect any interception of the key, whereas with courier the key security cannot be proven or tested. QKD (quantum key distribution) systems also have the advantage of being automatic, with greater reliability and lower operating costs than a secure human courier network.
In cryptanalysis and computer security, password cracking is the process of guessing passwords [1] protecting a computer system. A common approach ( brute-force attack ) is to repeatedly try guesses for the password and to check them against an available cryptographic hash of the password. [ 2 ]
Practicality depends on the input set size and the speed or cost of computing the hash function. A common example is the use of hashes to store password validation data for authentication. Rather than store the plaintext of user passwords, an access control system stores a hash of the password.
The salt and hash are then stored in the database. To later test if a password a user enters is correct, the same process can be performed on it (appending that user's salt to the password and calculating the resultant hash): if the result does not match the stored hash, it could not have been the correct password that was entered.
The added computational work makes password cracking much more difficult, and is known as key stretching. When the standard was written in the year 2000 the recommended minimum number of iterations was 1,000, but the parameter is intended to be increased over time as CPU speeds increase.