Asymmetric Key Pair
Definition
Mathematically linked public and private keys. The public key encrypts or verifies, the private key decrypts or signs. Two to three orders of magnitude slower than symmetric primitives, but no shared secret is needed in advance.
- Roles
- Public key encrypts/verifies, private key decrypts/signs
- Relative speed
- 2 to 3 orders of magnitude slower than symmetric
- Advantage
- No pre-shared secret required
- Mathematical basis
- Trapdoor functions
Common questions
If asymmetric keys are so much slower, why are they used at all in practice?+
Real systems typically use the asymmetric pair only to securely exchange or sign a symmetric session key, then switch to fast symmetric encryption for the bulk data, combining the asymmetric pair's no-shared-secret advantage with symmetric encryption's speed.
What happens to data encrypted with a public key if the matching private key is lost?+
The data becomes permanently unrecoverable through normal means, since only the corresponding private key can reverse the encryption; this is why private key backup and escrow procedures matter for any evidence or system relying on asymmetric encryption.
Related terms
- CIAN
- Confidentiality, Integrity, Authentication, Non-repudiation. The four properties a cryptosystem can deliver, usually not all at once with a single primitive. Bulk encryption...
- Confusion and Diffusion
- Shannon's 1949 design principles. Confusion makes the relationship between key and ciphertext as complex as possible; diffusion spreads each plaintext bit's influence...
- Hybrid Encryption
- The pattern every real protocol uses: asymmetric crypto exchanges a fresh symmetric session key, then the symmetric primitive does the heavy lifting...
- Perfect Forward Secrecy
- A property where compromise of a long-term key does not retroactively break past sessions, because each session used an ephemeral key (typically...
- Symmetric Key
- One shared secret used to both encrypt and decrypt. Fast (AES-128 on AES-NI runs at multiple GB/s) but solves nothing if the...