Planning for post-quantum cryptography: Impact, challenges and next steps

Symmetric vs. asymmetric cryptography

Encryption algorithms can be classified into one of two categories based on their use of encryption keys. Symmetric encryption algorithms use the same secret key for both encryption and decryption. Asymmetric or public-key encryption algorithms use a pair of related keys. Public keys are used for encryption and digital signature validation, while private keys are used for decryption and digital signature validation.

Different types of encryption algorithms have different benefits and downsides. For example, symmetric encryption algorithms are often more efficient, making them well-suited to bulk data encryption. However, they need the shared secret key to be shared between the sender and recipient over a secure channel before message encryption/decryption can be performed.

Asymmetric cryptography is less efficient but does not have this requirement. Encryption is performed using public keys, which, as their name suggests, are designed to be public. As a result, asymmetric algorithms are often used to create a secret channel over which a shared symmetric key is established for bulk data encryption.

Asymmetric cryptography and “hard” problems

Asymmetric encryption algorithms are built using a mathematically “hard” problem. This is a mathematical function where performing an operation is far easier than undoing it. For example,

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