Post-quantum cryptography: protecting the future of digital interactions

Post-quantum cryptography (PQC) refers to cryptographic algorithms specifically designed to resist attacks from quantum computers. These algorithms aim to protect our digital security even when quantum computers become powerful enough to break traditional cryptographic systems, such as RSA and ECC, which rely on the difficulty of factoring large numbers or computing discrete logarithms.

A cryptographically relevant quantum computer (CRQC) is a quantum computing system powerful enough to break current public-key cryptography. CRQCs utilize quantum algorithms, such as Shor’s algorithm, to efficiently solve complex mathematical problems like integer factorization, posing a significant risk to widely used public-key encryption schemes like RSA. Private-key encryption schemes such as AES are only affected by generic attacks like the Grover’s algorithm allowing for a quadratic speed-up of operations required to break them. Doubling the used key lengths can counteract this effect.

Current estimates by governments and security organizations suggest that cryptographically relevant quantum computers may emerge in the early to late 2030s. Though significant advancements in quantum error correction in recent years have been made, making an earlier arrival of cryptographically relevant quantum computers likely.

The advent of cryptographically relevant quantum computers poses significant risks to digital security as they have the potential to break the public-key cryptography currently in use. This could compromise the confidentiality and integrity of digital information, including personal data, financial transactions, government communications, and more. Thus, post-quantum cryptography is essential to safeguarding our digital security in the future.

Not all, but many commonly used cryptographic algorithms are vulnerable to the computational power of quantum computers. Public-key cryptography systems like RSA and ECC, which rely on the difficulty of factoring large numbers or solving discrete logarithms, could be broken by quantum algorithms such as Shor's algorithm. Symmetric cryptographic algorithms like AES are also affected, but to a lesser extent, as their security can be increased by using longer key lengths.

Public-key cryptography, also known as asymmetric cryptography, is a cryptographic system that uses a pair of keys: a public key, which is publicly known and accessible, and a private key, which is kept secret and only known to the owner. The public key is used to encrypt data, while the private key is used to decrypt it. This ensures that only the intended recipient, who possesses the private key, can access the original message. Public-key cryptography is widely used for secure communication over the internet, including for encrypting emails, digital signatures, and securing online transactions.

Private-key cryptography, also known as symmetric cryptography, is a type of encryption where the same key is used for both encrypting and decrypting messages. This key must be shared and kept secret between the communicating parties. The process involves converting plaintext into ciphertext using the secret key, ensuring that only those who have the key can decrypt the message back into plaintext and read it. This method of cryptography is efficient and is widely used for securing data transmission and storage where the key can be kept secure.

Cryptography relies on the difficulty of complex mathematical problems, in traditional public-key cryptography that is the difficulty of factorization or solving the discrete logarithm problem. A traditional computer would need 100,000 of years to solve these problems, a powerful quantum computer only seconds to days. PQC algorithms are specifically designed to remain secure even against attacks by powerful quantum computers as their underlying mathematical problems are of a different nature.

The primary quantum computing threat to your business today are "store now, decrypt later" attacks. This involves malicious actors collecting and storing encrypted data to decrypt it once powerful quantum computers are available. Such attacks are mainly relevant for very sensitive information, especially governmental data or state secrets. Real-time attacks like authenticating to a digital service will only be relevant once cryptographically relevant quantum computers are available. To be prepared in time against future threats by quantum computers, businesses should establish their PQC migration strategy now.