🔐RSA

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Also known as: Rivest Shamir Adleman

A public-key cryptosystem for encryption and signatures based on the hardness of integer factorization.

DESCRIPTION

RSA is a foundational asymmetric cryptosystem using modular exponentiation with a composite modulus n = p·q. It supports encryption, key transport, and digital signatures with schemes like OAEP and PSS standardized in PKCS#1. Security depends on sufficiently large keys, correct padding, and robust parameter choices. RSA underpins TLS handshakes, code signing, and certificate infrastructures. Modern practice favors RSA for compatibility while promoting elliptic-curve alternatives for performance and smaller keys. Misuse, such as raw RSA or weak padding, leads to severe vulnerabilities.

ALTERNATIVE DEFINITIONS

Wikipedia

RSA is a public-key cryptosystem that is widely used for secure data transmission. It is based on the complexity of factoring large integers.

Highlights widespread use and factorization-based security.

Source

IETF RFC 8017

This document specifies version 2.2 of PKCS #1, RSA Cryptography Specifications, which includes definitions of RSA public and private key formats and the RSA-based encryption and signature schemes.

Defines standardized padding schemes and key formats for RSA.

Source

RELATED TERMS

Asymmetric Encryption PKCS #1 RSA-OAEP RSA-PSS Diffie–Hellman Key Exchange X.509 Certificate TLS SHA-256 Key Length

COMPETING TERMS

Elliptic Curve Cryptography

KNOWLEDGE AREAS

Data Security Mathematics

TARGET AUDIENCE

Cybersecurity Engineer Security Architect Software Developer Chief Information Security Officer

EXTERNAL SOURCES

• Wikipedia - RSA (cryptosystem)
• IETF RFC 8017 - PKCS#1 v2.2 RSA specifications and padding schemes.
• NIST - Key management recommendations for RSA and related schemes.

TOP QUESTIONS

Why is RSA still relevant?

It remains widely deployed for compatibility in TLS, code signing, and PKI, despite performance advantages of elliptic-curve cryptography.

Category: Relevancy

What is the biggest risk when using RSA?

Improper padding or small key sizes enable attacks; follow PKCS#1 OAEP and PSS with strong key lengths.

Category: Risks

What key sizes are recommended for RSA?

2048-bit minimum for general use; 3072-bit or 4096-bit for long-term security depending on policy.

Category: Requirements

How does RSA compare to Elliptic Curve Cryptography?

ECC achieves equivalent security with smaller keys and faster operations; RSA is simpler and more ubiquitous.

Category: Alternatives

What are common mistakes using RSA?

Using raw RSA, deterministic padding, or rolling custom implementations instead of standardized libraries.

Category: Mistakes

Where is RSA used in TLS 1.3?

Primarily for certificate signatures; key exchange in TLS 1.3 uses ephemeral Diffie–Hellman for forward secrecy.

Category: Example

Who invented RSA?

Ron Rivest, Adi Shamir, and Leonard Adleman introduced RSA in 1977.

Category: Example

What is OAEP in RSA?

Optimal Asymmetric Encryption Padding provides randomized padding for secure RSA encryption.

Category: Example

How is RSA managed operationally?

Use vetted libraries, enforce key rotation, strong padding schemes, and certificate lifecycle management.

Category: Management