RSA
Definition
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 (NIST recommended beyond 2030).
- Named for
- Rivest, Shamir, Adleman
- Introduced
- 1977
- Basis
- Difficulty of factoring large prime products
- Standard key size
- 2048-bit
- NIST recommendation beyond 2030
- 3072-bit
Common questions
What forensic role does RSA play in an investigation?+
Examiners encounter RSA in digital signatures, encrypted containers, TLS certificates, and PKI chains recovered from a device or network capture. Its presence can indicate authenticated communication or encrypted evidence that cannot be read without the private key.
Why does key size matter when assessing RSA in a case?+
Shorter keys such as 1024-bit are considered breakable with sufficient computing resources and are being phased out, so the key size found on a device affects how confidently an examiner can treat RSA-protected data as inaccessible without the key.
How is RSA different from AES for an examiner to note?+
RSA is asymmetric, using a public and private key pair for signing or key exchange, while AES is symmetric, using one shared key to encrypt bulk data. Systems typically use RSA to exchange or protect an AES key rather than to encrypt large volumes of data directly.
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...
- PKI
- Public Key Infrastructure. The set of roles (CA, RA, VA) and artefacts (X.509 certificates, CRL, OCSP) that bind a public key to...
- 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...