Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesSymmetric encryption uses one shared secret key; asymmetric cryptography uses a related public and private key pair. Neither is a universal substitute for the other: systems can combine them, and the right choice depends on the operation, key handling, protocol, and security goal.
How symmetric encryption works
Alice and Bob both need the same secret key. Alice uses it to encrypt a message, and Bob uses that key to decrypt it. The key must stay secret and be securely made available to every party that needs it. NIST defines a symmetric-key algorithm as one that uses “the same secret key for an operation and its complement (e.g., encryption and decryption).” NIST’s symmetric-key glossary provides the formal definition.
AES: a recognized example
The Advanced Encryption Standard (AES) is a symmetric block cipher used to encrypt and decrypt information. The NIST standard specifies 128-, 192-, and 256-bit keys, with a 128-bit block size. These are the algorithm’s defined sizes, not measurements of speed or a direct comparison with public-key sizes. NIST’s AES publication dates to 2001; the 2023 update to FIPS 197 made editorial improvements and no technical change to the algorithm.
How asymmetric cryptography works
Asymmetric cryptography uses two related keys: a public key and a private key. In an encryption example, a sender encrypts information with the recipient’s public key, and the recipient decrypts it with the corresponding private key. The public key can be shared; the private key must be protected.
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Encryption is not the same as signing
A key pair can also support digital signatures: the private key creates a signature, and the corresponding public key verifies it. This is a different operation from encryption. Encryption is used for confidentiality; signatures can help verify origin and integrity, subject to the scheme and protocol. Not every asymmetric algorithm performs both jobs. See NIST’s public-key cryptography glossary and its asymmetric-key cryptography glossary.
What to compare when choosing an approach
| Decision factor | Questions to ask |
|---|---|
| Operation | Do you need to encrypt data, establish or agree on a key, or create and verify a digital signature? |
| Key handling | How will parties securely distribute and protect a shared secret, or protect a private key and manage public keys? |
| Protocol and implementation | What does the system support, and what do current protocol and platform guidance require? |
| Purpose and threat model | Is the required property confidentiality, verification, or both, and what risks must the design address? |
Key generation and handling are part of the security design, not an afterthought. NIST SP 800-133 Rev. 2 (2020) covers generating keys used by approved cryptographic algorithms; consult its key-generation guidance alongside the applicable system requirements.
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Why deployed systems can use both
A real protocol does not necessarily choose one family exclusively. Symmetric and asymmetric techniques can have different roles within the same system, so assess what each operation does and how keys are managed rather than labeling an entire design as one type of encryption. TLS is one useful context for evaluating cryptographic algorithms and configuration. NIST SP 800-52 Rev. 2 (2019) provides guidance on selecting and configuring TLS implementations using FIPS and NIST-recommended algorithms. For an actual deployment, follow the current standards and documentation for the relevant protocol and platform; this guidance is not a cipher-suite recommendation.
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