RSA (Rivest-Shamir-Adleman) encryption is widely used and considered secure against classical computers when used with sufficiently large key sizes. However, the security of RSA, as well as many other asymmetric encryption algorithms, is threatened by the advent of large-scale quantum computers.
Quantum computers have the potential to significantly impact the field of cryptography by breaking certain types of algorithms that rely on the difficulty of factoring large numbers or computing discrete logarithms, which includes RSA. Shor's algorithm, a quantum algorithm discovered by Peter Shor in 1994, can efficiently factor large numbers and solve the discrete logarithm problem on a quantum computer, rendering RSA vulnerable.
If a working quantum computer with a sufficient number of qubits and error correction capabilities becomes available, it could potentially break RSA and other asymmetric encryption algorithms by leveraging Shor's algorithm. This would allow the quantum computer to quickly factor the large numbers involved in RSA encryption and reveal the private key.
To counteract this threat, there is ongoing research into developing quantum-resistant encryption algorithms, also known as post-quantum cryptography. These algorithms aim to provide security against attacks by both classical and quantum computers. The National Institute of Standards and Technology (NIST) in the United States has been running a competition to select new quantum-resistant cryptographic algorithms, and the process is still ongoing.
It's important to note that the development and widespread adoption of practical quantum computers capable of breaking RSA and other widely used encryption algorithms is still a significant technological challenge. The timeline for achieving such a capability remains uncertain. Nonetheless, the potential impact of quantum computers on traditional cryptographic systems is an active area of research, and preparations are being made to transition to quantum-resistant algorithms in the future.