SSCP Cryptography Practice Question
An organization is planning to implement ECC for digital signatures. Which key size provides a security level equivalent to a 3072-bit RSA key?
⚠ Common exam trap
A common mix-up: candidates confuse symmetric key equivalence (e.g., 256-bit ECC matches 128-bit symmetric) with RSA equivalence, or mistakenly think larger ECC keys (like 384-bit) are needed to match 3072-bit RSA, when in fact 256-bit ECC is the correct match per NIST guidelines.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
256-bit ECC
The National Institute of Standards and Technology (NIST) recommends that a 256-bit elliptic curve (e.g., P-256) provides a security strength of 128 bits, which is equivalent to a 3072-bit RSA key. This equivalence is based on the computational difficulty of the discrete logarithm problem in elliptic curve groups versus integer factorization, where ECC requires significantly smaller key sizes for the same security level.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
192-bit ECC
Why it's wrong here
192-bit ECC delivers roughly 96 bits of security, matching a 2048-bit RSA key rather than 3072-bit. It tempts because 192-bit curves such as NIST P-192 exist and suit legacy interoperability, but the equivalence table pairs 3072-bit RSA with 256-bit ECC.
- ✓
256-bit ECC
Why this is correct
ECC delivers roughly half the key length of RSA for equivalent strength: a 256-bit ECC key matches 3072-bit RSA. This satisfies the stem's requirement for a 3072-bit RSA security equivalence, giving the same protection with far smaller keys and faster computation.
- ✗
1024-bit ECC
Why it's wrong here
1024-bit ECC delivers roughly 80-bit security, matching a 2048-bit RSA key, so it falls short of the 3072-bit RSA equivalence sought. It is tempting because 1024-bit keys are common in legacy RSA deployments, but ECC's smaller key sizes mean this pairing is mismatched.
- ✗
384-bit ECC
Why it's wrong here
384-bit ECC actually provides security equivalent to a 7680-bit RSA key, exceeding the 3072-bit target. It is tempting because 384-bit ECC is a widely deployed standard curve size, but the question asks for the 3072-bit RSA equivalence, which 256-bit ECC satisfies.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SSCP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SSCP exam.