Overview
Domain 9 covers cryptography in one module. It covers cryptographic concepts and the difference between symmetric and asymmetric encryption, specific algorithms such as AES, DES, 3DES, RSA and elliptic curve cryptography, hashing algorithms and their properties, public key infrastructure and digital certificates, disk and email encryption, and cryptanalysis and cryptographic attacks such as known-plaintext, chosen-plaintext and brute-force attacks, plus cryptography tools and countermeasures.
Although only 5% of the exam, cryptography is consistently the lowest-scoring domain in candidate practice data. Most CEH candidates come from networking or operations backgrounds where cryptography is a black box, and the exam expects them to understand the internals. The difference between scoring poorly and well on these six questions can be the difference between passing and failing, so the domain deserves attention well beyond its weight.
How it's tested
Expect concise but deep questions: classifying an algorithm, choosing the right cryptographic tool for a goal, identifying a PKI element, or recognizing a cryptanalysis attack from its description. The questions test internals more than the weight suggests. Read the full scenario and every option carefully before deciding.
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Classify the algorithm
An algorithm or requirement is described, and you must identify it as symmetric or asymmetric or match it to a use.
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Goal to mechanism
A goal such as confidentiality, integrity or non-repudiation is stated, and you must choose hashing, symmetric or asymmetric encryption, or a digital signature.
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Identify the attack
A cryptanalysis scenario is described, and you must name the attack, such as known-plaintext or chosen-plaintext.
A system needs to let two parties who have never met exchange encrypted messages without sharing a key in advance, and prove who sent each message. Symmetric encryption needs a pre-shared key, which they lack. Asymmetric encryption solves key exchange and, through digital signatures, proves the sender, so the answer uses asymmetric cryptography rather than a symmetric cipher alone.
Domains 1
Official domains from the EC-Council outline, in outline order.
9.1 CryptographySymmetric and asymmetric encryption, hashing, PKI, disk and email encryption, and cryptanalysis.
- What it means
- This module covers cryptographic concepts, symmetric encryption (AES, DES, 3DES) and asymmetric encryption (RSA, elliptic curve cryptography), hashing algorithms (such as SHA family and MD5) and their collision resistance, public key infrastructure including certificate authorities and digital certificates, digital signatures, disk encryption and email encryption (PGP, S/MIME), and cryptanalysis and cryptographic attacks (known-plaintext, chosen-plaintext, ciphertext-only, related-key, brute-force, birthday and padding attacks), with tools and countermeasures.
- What to understand
- Symmetric encryption uses one shared key and is fast, while asymmetric uses a key pair and solves key distribution and enables digital signatures; the two are usually combined. Hashing is one-way and provides integrity, not confidentiality. A digital signature uses the sender's private key and provides integrity, authenticity and non-repudiation. Cryptanalysis attacks are distinguished by what the attacker has access to, such as known or chosen plaintext.
- How it shows up
- An algorithm, goal, PKI element or attack is described, and you must classify it, match it to a use, or name the attack.
- Common confusion
- Confusing hashing with encryption. Hashing is one-way and for integrity; encryption is reversible and for confidentiality.
High-yield concepts
The terms, rules and formulas this domain turns into questions most often.
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Symmetric vs. asymmetric
Symmetric uses one shared key and is fast; asymmetric uses a key pair and solves key distribution.
- Remember
- They are usually combined, with asymmetric exchanging a symmetric key.
- Tested as
- Classification questions.
- Trap
- Using asymmetric for bulk data.
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Which key does what
Encrypt for confidentiality with the recipient's public key; sign with the sender's private key.
- Remember
- Private keys sign and decrypt; public keys encrypt and verify.
- Tested as
- Key usage questions.
- Trap
- Signing with a public key.
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Hashing
A one-way function producing a fixed-length digest.
- Remember
- It provides integrity, not confidentiality, and is not reversible.
- Tested as
- Integrity questions.
- Trap
- Treating hashing as encryption.
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Digital signature
A hash signed with the sender's private key.
- Remember
- It provides integrity, authenticity and non-repudiation.
- Tested as
- Non-repudiation questions.
- Trap
- Expecting it to provide confidentiality.
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AES vs. DES vs. 3DES
AES is the current symmetric standard; DES is obsolete and 3DES is legacy.
- Remember
- Prefer AES; DES is broken.
- Tested as
- Algorithm questions.
- Trap
- Treating DES as still secure.
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RSA vs. ECC
Both are asymmetric; ECC offers comparable strength with shorter keys.
- Remember
- ECC is efficient for constrained devices.
- Tested as
- Algorithm questions.
- Trap
- Comparing key lengths across symmetric and asymmetric algorithms directly.
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PKI and certificates
Certificate authorities bind public keys to identities through digital certificates.
- Remember
- Trust flows from the CA, and revocation is checked via CRL or OCSP.
- Tested as
- PKI questions.
- Trap
- Confusing certificate expiry with revocation.
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Forward secrecy
Compromising a long-term key does not expose past session traffic.
- Remember
- It relies on ephemeral session keys.
- Tested as
- Advanced crypto questions.
- Trap
- Assuming one key compromise exposes only future traffic.
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Cryptanalysis attack types
Known-plaintext, chosen-plaintext, ciphertext-only and related-key, defined by what the attacker has.
- Remember
- The attacker's access defines the attack.
- Tested as
- Cryptanalysis questions.
- Trap
- Confusing known-plaintext with chosen-plaintext.
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Birthday attack
Exploits hash collision probability to find two inputs with the same hash.
- Remember
- It targets hash collision resistance.
- Tested as
- Cryptanalysis questions.
- Trap
- Confusing it with brute force.
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PGP and S/MIME
Email encryption schemes; PGP uses a web of trust, S/MIME uses PKI certificates.
- Remember
- Both provide email confidentiality and signing.
- Tested as
- Email encryption questions.
- Trap
- Confusing their trust models.
Side by side
Concepts candidates mix up, compared on the point that decides the answer.
Symmetric vs. asymmetric encryption
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Symmetric | One shared key, fast | Bulk encryption, hard key distribution | Sharing keys over insecure channels |
| Asymmetric | Public and private key pair | Solves key exchange, enables signatures, slower | Using it for large data volumes |
Hashing vs. encryption vs. digital signature
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Hashing | One-way digest | Integrity only, no key | Using it for confidentiality |
| Encryption | Reversible transformation with a key | Confidentiality | Assuming it proves the sender |
| Digital signature | Hash signed with a private key | Integrity, authenticity and non-repudiation | Expecting confidentiality |
Known-plaintext vs. chosen-plaintext vs. ciphertext-only
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Known-plaintext | Attacker has some plaintext and its ciphertext | Plaintext is known, not chosen | Confusing it with chosen-plaintext |
| Chosen-plaintext | Attacker can encrypt chosen plaintext | Attacker controls the input | Confusing it with known-plaintext |
| Ciphertext-only | Attacker has only ciphertext | Least information available | Overestimating what it allows |
Exam traps
Each trap is an answer that looks right. Learn the clue that should change your mind.
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Hash for confidentiality
- What candidates pick
- Hash sensitive data to keep it secret.
- Why it looks right
- Hashes look unreadable.
- Why it's wrong
- Hashing is one-way and for integrity. Confidentiality requires encryption.
Clue to watch for The data must be recovered or kept secret, not just verified.
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Symmetric for signing
- What candidates pick
- Use a shared symmetric key to provide non-repudiation.
- Why it looks right
- Symmetric encryption is fast and simple.
- Why it's wrong
- Both parties share the key, so neither can be uniquely bound to a message. A digital signature with a private key is needed.
Clue to watch for The requirement is proof of origin the sender cannot deny.
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Sign with the public key
- What candidates pick
- Sign a message with the recipient's public key.
- Why it looks right
- Public keys are used in encryption.
- Why it's wrong
- Signing uses the sender's private key; verification uses the sender's public key.
Clue to watch for The goal is proving who sent something.
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DES is fine
- What candidates pick
- Recommend DES for new encryption.
- Why it looks right
- It is a well-known algorithm.
- Why it's wrong
- DES is obsolete and broken. AES is the current standard.
Clue to watch for The question asks for a secure, modern algorithm.
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Asymmetric for bulk data
- What candidates pick
- Encrypt large volumes of data directly with RSA.
- Why it looks right
- Asymmetric encryption is strong.
- Why it's wrong
- Asymmetric encryption is slow. In practice it exchanges a symmetric key, which then encrypts the bulk data.
Clue to watch for The scenario involves encrypting large amounts of data.
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Known equals chosen plaintext
- What candidates pick
- Call an attack where the attacker picks the plaintext a known-plaintext attack.
- Why it looks right
- Both involve plaintext.
- Why it's wrong
- If the attacker chooses the plaintext to be encrypted, it is a chosen-plaintext attack.
Clue to watch for The attacker controls which plaintext is encrypted.
Answer framework
For any Domain 9 cryptography scenario, use these steps before choosing an answer.
- State the goal precisely, whether confidentiality, integrity, authenticity or non-repudiation, since each points to a different mechanism.
- Choose the mechanism that delivers that goal, using hashing for integrity, encryption for confidentiality and digital signatures for non-repudiation.
- Decide whether symmetric or asymmetric cryptography fits, remembering asymmetric solves key exchange and enables signatures while symmetric handles bulk data efficiently.
- Work out which key is used, with the sender's private key signing and the recipient's public key encrypting for confidentiality.
- For cryptanalysis, classify the attack by what the attacker has access to, distinguishing known-plaintext, chosen-plaintext and ciphertext-only, and confirm which key performs each operation.
Practice question
Want more like this? The CEH practice test has questions for every domain.
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Study strategy
Treat this small domain as if it were much larger, because it is the lowest-scoring section for most candidates and the questions are deep. Start with the core distinctions: symmetric versus asymmetric, hashing versus encryption, and which key signs versus encrypts. Build a table mapping each goal, confidentiality, integrity, authenticity and non-repudiation, to the right mechanism, and drill the which-key question until it is automatic.
Next, learn the algorithms by role and status: AES as the current symmetric standard, DES as broken, RSA and ECC as asymmetric, and the hash families. Then study PKI, certificates and revocation, and the email schemes PGP and S/MIME with their trust models.
Finally, give cryptanalysis real attention, because it is where the hardest questions sit. Learn to classify attacks by what the attacker has, and recognize the birthday attack against hashes. Do not skim this domain to save time for larger ones; the points here are easy to lose and hard to recover. This is the final domain, so finish by taking full-length practice exams to balance across all nine.
FAQ
How much of CEH v13 is Domain 9?
Cryptography is about 5% of the exam, roughly six questions, but it is the lowest-scoring domain for most candidates.
Why do candidates struggle with cryptography if it is only 5%?
The questions test internals, not just algorithm names. Many candidates come from backgrounds where cryptography is a black box, so they lose points that are hard to recover elsewhere.
What is the difference between hashing and encryption?
Hashing is one-way and provides integrity. Encryption is reversible and provides confidentiality. Hashing cannot be used to recover the original data.
Which key signs a message?
The sender's private key. Anyone can verify the signature with the sender's public key, which provides authenticity and non-repudiation.
Is DES still secure?
No. DES is obsolete and broken. AES is the current symmetric standard, and 3DES is only legacy.
What distinguishes the cryptanalysis attack types?
What the attacker has access to. Known-plaintext means they have plaintext and its ciphertext; chosen-plaintext means they can encrypt plaintext they choose; ciphertext-only means they have only ciphertext.
How does Domain 9 connect to the rest of the exam?
Cryptography underpins secure protocols, PKI, email and disk encryption, and the defenses referenced across the network, web, wireless and cloud domains.
Other Cybersecurity certifications
Where the same subject shows up in other exams. Cards marked "Same subject" open the matching domain.
- Systems Security Certified Practitioner Same subject: Domain 5: Cryptography (9%)
- CompTIA Cybersecurity Analyst+ Study guide
- Microsoft Security Operations Analyst Associate Study guide
- Penetration Tester Study guide
- Certified in Risk and Information Systems Control Study guide
- CompTIA PenTest+ Study guide
- CompTIA SecurityX (CASP+) Study guide
- Azure Security Engineer Associate Study guide
- CISM (Certified Information Security Manager) Study guide
- CISSP Study guide
- CompTIA Security+ Study guide
- Certified Information Systems Auditor Study guide
- Certified Cloud Security Professional Study guide
Test your Domain 9 knowledge
You have covered symmetric and asymmetric encryption, hashing, PKI, email and disk encryption, and cryptanalysis. Test whether you can match goals to mechanisms and classify attacks under exam conditions.