PKI
Definition
Public Key Infrastructure. The set of roles (CA, RA, VA) and artefacts (X.509 certificates, CRL, OCSP) that bind a public key to a real-world identity.
- Full name
- Public Key Infrastructure
- Core roles
- Certificate Authority, Registration Authority, Validation Authority
- Key artefact
- X.509 digital certificate
- Revocation checks
- Certificate Revocation List and OCSP
Common questions
What does PKI actually prove in a digital evidence context?+
It links a public key to a verified real-world identity through a chain of trust ending at a Certificate Authority, so a digital signature made with the matching private key can be tied to that identity rather than proving the identity acted honestly or was not compromised.
Why does an investigator need to check certificate revocation status, not just the certificate itself?+
A certificate that was valid when issued can later be revoked because the private key was compromised or the holder's details changed, so relying on an unrevoked-at-signing-time check via CRL or OCSP is necessary to trust a signature's validity at the time it was made.
Related terms
- Asymmetric Cryptography
- Cryptosystem that uses a key pair: a public key (shareable) and a private key (secret). Built on mathematical trapdoor functions where the...
- Digital Signature
- Cryptographic proof of authenticity, integrity and non-repudiation. Sign by encrypting a hash of the message with the signer's private key; verify by...
- DSC
- Digital Signature Certificate. An Indian X.509 certificate issued by a CCA-licensed CA. Class 3 is the current mandatory tier for income tax,...
- ECC
- Elliptic Curve Cryptography. Smaller keys for equivalent security; 256-bit ECC is roughly equivalent to 3072-bit RSA. Used in ECDSA signatures, ECDH key...
- Hash Function
- Deterministic function that maps an input of arbitrary length to a fixed-length output. A cryptographic hash adds pre-image resistance, second pre-image resistance,...
- HMAC
- Hash-based Message Authentication Code, RFC 2104. Combines a secret key with a hash function to produce a MAC; immune to the length-extension...
- RSA
- Rivest-Shamir-Adleman, 1977. Public-key cryptosystem based on the hardness of factoring a product of two large primes. Common sizes today: 2048-bit (standard), 3072-bit...
- Trapdoor Function
- A one-way function with a secret 'trapdoor' that makes the reverse direction tractable. RSA's trapdoor is the factorisation of n into p...