Determine equivalent security strength for RSA key sizes. RSA-2048 equals 112-bit, 3072 equals 128-bit, 4096 equals 152-bit security.
RSA key size directly determines the security level of RSA encryption and digital signatures. However, RSA key bits do not map one-to-one with security bits — RSA-2048 provides only about 112 bits of security, not 2048. This is because RSA can be attacked more efficiently than brute force using number field sieve algorithms for factoring large numbers.
This calculator shows the equivalent security strength in bits for any RSA key size, along with the corresponding AES and ECC key sizes that provide equal protection. It helps certificate administrators, security architects, and developers choose appropriate RSA key sizes and plan migrations to stronger keys or alternative algorithms like ECC.
Understanding this metric in precise terms allows technology leaders to make evidence-based decisions about scaling, architecture, and infrastructure investment priorities for their organizations. Tracking this metric consistently enables technology teams to identify system performance trends and address potential issues before they impact end users or business operations.
RSA key size recommendations change over time as computing power increases and cryptanalysis improves. Understanding the actual security level helps you avoid both under-provisioning (RSA-1024 is broken) and over-provisioning (RSA-8192 is extremely slow). This calculator provides the concrete numbers needed for informed decisions. Consistent measurement creates a reliable baseline for tracking system health over time and identifying degradation before it impacts users or triggers costly production outages.
Approximate RSA security bits using GNFS: security ≈ 1.923 × (key_bits)^(1/3) × (ln(key_bits))^(2/3) − 4.69 (simplified NIST mapping). RSA-1024≈80-bit, RSA-2048≈112-bit, RSA-3072≈128-bit, RSA-4096≈152-bit, RSA-7680≈192-bit, RSA-15360≈256-bit.
Result: 112-bit security | AES-112 | ECC-224
RSA-2048 provides approximately 112 bits of security. While still acceptable for near-term use, NIST recommends migrating to RSA-3072 (128-bit security) for data that must remain protected beyond 2030. The equivalent ECC key size is P-224, though P-256 is the practical minimum used today.
The security of RSA depends on the difficulty of factoring large numbers using the General Number Field Sieve (GNFS). NIST publishes recommended key sizes based on projected advances in both algorithmic techniques and hardware capabilities.
RSA-1024 was deprecated in 2013 after achieving only 80-bit security. RSA-2048 has been the standard minimum since then, providing 112-bit security. NIST recommends transitioning to RSA-3072 (128-bit) for use beyond 2030.
RSA operations are computationally expensive. Encryption and signature verification are relatively fast (public key operations), but decryption and signing (private key operations) scale roughly with the cube of the key size. RSA-4096 private key operations are approximately 8× slower than RSA-2048.
ECC P-256 provides 128-bit security with 256-bit keys, matching RSA-3072 while being 10–20× faster for signing operations. Most modern TLS implementations prefer ECC certificates, and major browsers and servers have supported ECDSA for years.
RSA-2048 is currently safe for most purposes and is expected to remain so until approximately 2030. However, for long-lived keys or highly sensitive data, NIST recommends RSA-3072 or higher. If quantum computers become practical, RSA of any size will be broken.
RSA can be attacked using the General Number Field Sieve (GNFS) algorithm, which is much faster than brute force. GNFS has sub-exponential complexity, meaning each doubling of key size adds less than a doubling of security. This is fundamentally different from symmetric algorithms like AES.
For certificates expiring within 5 years, RSA-2048 is acceptable. For 10+ year validity, use RSA-3072 or RSA-4096. Better yet, consider ECC P-256 or P-384 certificates, which provide equal or better security with dramatically better performance.
RSA-2048 generation takes about 0.1–0.5 seconds. RSA-4096 takes 1–5 seconds. RSA-8192 can take 30–60 seconds or more depending on the hardware. This is a one-time cost but significant for applications generating many keys.
Yes, Shor's algorithm on a sufficiently powerful quantum computer can factor RSA keys of any size in polynomial time. Current estimates suggest a cryptographically relevant quantum computer could emerge between 2030 and 2040. Organizations should plan migration to post-quantum algorithms.
RSA-8192 is rarely justified. It provides approximately 200-bit security but is extremely slow for key generation and operations. AES-256 or ECC-384 provide comparable or better security with vastly better performance. Use RSA-4096 as the practical maximum if RSA is required.