Overview
Domain 5 covers the practitioner's working knowledge of cryptography. It starts with the reasons for it: confidentiality, integrity and authenticity, the sensitivity of data such as PII, intellectual property and PHI, regulatory and industry requirements such as PCI DSS and ISO standards, and entropy, including quantum cryptography and quantum key distribution. It covers applying concepts: hashing, salting, symmetric and asymmetric encryption, elliptic curve cryptography, non-repudiation through digital signatures, certificates, HMAC and audit trails, the strength of algorithms and keys such as AES and RSA, and cryptographic attacks. It then covers secure protocols with their use cases and limitations, and public key infrastructure, including key management and the web of trust.
The domain supports almost every other one. Access control relies on certificates, network security on TLS, IPsec and VPNs, and incident response on hashing evidence.
How it's tested
Questions describe a protection need, a protocol choice or a key management situation and ask which algorithm, key or protocol BEST fits, or what weakness a configuration has. Expect practical framing, such as configuring a VPN or protecting stored passwords, rather than mathematics.
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Goal to tool
A goal such as confidentiality, integrity, authenticity or non-repudiation is stated, and you must pick hashing, symmetric or asymmetric encryption, HMAC or a digital signature.
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Which key?
You must decide whose public or private key is used to encrypt, decrypt, sign or verify.
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Protocol and PKI operations
A protocol, certificate or key life cycle event is described, such as revocation, rotation or escrow, and you must choose the right action.
A company must prove that contracts sent to customers came from it and were not changed, and that it cannot later deny sending them. HMAC proves integrity, but both parties hold the shared key, so either could have produced it. Encrypting with the customer's public key gives confidentiality, not proof of origin. A digital signature with the company's private key, verified with its public key, provides integrity, authenticity and non-repudiation.
Subdomains 4
Official subdomains from the ISC2 outline, in outline order.
5.1 Understand reasons and requirements for cryptographyConfidentiality, integrity and authenticity, data sensitivity, regulation and entropy.
- What it means
- Cryptography protects confidentiality, integrity and authenticity. Requirements come from data sensitivity (PII, intellectual property, PHI) and from regulation and industry practice such as PCI DSS and ISO standards. Entropy, the randomness behind keys, is essential, and the outline also mentions quantum cryptography and quantum key distribution.
- What to understand
- Choose cryptography to match the goal and the data's sensitivity. Weak randomness produces predictable keys, which undermines even strong algorithms. Large-scale quantum computing would threaten today's public key algorithms such as RSA and ECC, which is why post-quantum algorithms are being standardized.
- How it shows up
- Questions ask which requirement drives the use of encryption for a data set, or why poor entropy is a risk.
- Common confusion
- Treating quantum key distribution as the same thing as post-quantum cryptography. QKD uses quantum physics to exchange keys, while post-quantum cryptography uses new mathematical algorithms that resist quantum attack.
5.2 Apply cryptography conceptsHashing, salting, symmetric and asymmetric encryption, non-repudiation, strength and attacks.
- What it means
- Hashing produces a fixed-length digest for integrity checking. Salting adds random data to passwords before hashing to defeat precomputed attacks. Symmetric encryption such as AES uses one shared key and is fast. Asymmetric encryption such as RSA and ECC uses key pairs and solves key distribution. Non-repudiation relies on digital signatures, certificates and audit trails. The outline also covers algorithm and key strength and common attacks.
- What to understand
- Symmetric and asymmetric encryption are usually combined: asymmetric to exchange a symmetric session key, symmetric for bulk data. HMAC provides integrity and authenticity with a shared key, but because both parties hold that key it cannot prove which one created a message, so true non-repudiation needs a digital signature. Common attacks include brute force, dictionary and rainbow table attacks on passwords, birthday attacks on hashes, and side-channel attacks.
- How it shows up
- A goal is stated and you must pick the mechanism, or a configuration is described and you must spot the weakness, such as unsalted password hashes.
- Common confusion
- Encrypting passwords rather than hashing them with a salt. Stored passwords should not be decryptable.
5.3 Understand and implement secure protocolsServices and protocols, common use cases, and limitations.
- What it means
- Secure protocols apply cryptography to real communications. Examples include TLS for web and application traffic, IPsec and VPNs for network tunnels, SSH and SFTP for administration and file transfer, S/MIME for email, and DKIM for email domain authentication. Use cases include card processing, file transfer, web clients, VPNs and transmission of PII.
- What to understand
- Each protocol protects a specific layer and use. Outdated versions such as SSL and early TLS should be disabled, and TLS 1.2 or 1.3 used. IPsec offers authentication headers (AH) for integrity and encapsulating security payload (ESP) for confidentiality, in transport or tunnel mode. DKIM signs mail to prove the sending domain but does not encrypt it.
- How it shows up
- A use case is described and you must choose the protocol, or a configuration is described and you must identify its limitation.
- Common confusion
- Assuming DKIM or digital signatures make email confidential. They authenticate the sender, and S/MIME encryption or TLS is needed for confidentiality.
5.4 Understand public key infrastructure (PKI)Key management concepts and the web of trust.
- What it means
- PKI uses certificate authorities to bind public keys to identities through certificates. Key management covers generation, storage, rotation, composition, exchange, revocation, escrow and destruction. A web of trust, used by PGP and GPG, relies on users vouching for each other's keys rather than a central authority.
- What to understand
- Private keys must be protected, because their compromise breaks every guarantee. Compromised certificates must be revoked and checked through certificate revocation lists (CRL) or the Online Certificate Status Protocol (OCSP). Key escrow lets authorized parties recover keys but creates its own risk if the escrow is compromised.
- How it shows up
- A private key is compromised, a certificate expires, or a key must be recoverable, and you must choose the correct PKI action.
- Common confusion
- Treating certificate expiry and revocation as the same. Expiry is planned end of validity, and revocation cancels a certificate early because it can no longer be trusted.
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 public and private key pair and solves key distribution.
- Remember
- They are combined in practice, with asymmetric used to exchange a symmetric session key.
- Tested as
- Algorithm selection questions.
- Trap
- Using asymmetric encryption 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, and verify with the sender's public 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
- Used for integrity checks and password storage, not reversible encryption.
- Tested as
- Integrity questions.
- Trap
- Calling it encryption.
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Salting
Adding unique random data to each password before hashing.
- Remember
- Defeats rainbow tables and makes identical passwords hash differently.
- Tested as
- Password storage questions.
- Trap
- Thinking salt must be kept secret.
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HMAC vs. digital signature
HMAC uses a shared secret key to prove integrity and authenticity. A digital signature uses a private key.
- Remember
- Only the signature provides true non-repudiation, because the private key belongs to one party.
- Tested as
- Non-repudiation questions.
- Trap
- Choosing HMAC for non-repudiation.
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AES vs. RSA vs. ECC
AES is symmetric. RSA and ECC are asymmetric.
- Remember
- ECC offers comparable strength to RSA with much shorter keys.
- Tested as
- Algorithm strength questions.
- Trap
- Comparing key lengths across symmetric and asymmetric algorithms directly.
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Rainbow table
A precomputed table of hashes used to reverse unsalted password hashes.
- Remember
- Salting defeats it.
- Tested as
- Attack questions.
- Trap
- Choosing longer passwords alone as the fix for stored hashes.
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TLS versions
TLS secures traffic between clients and servers.
- Remember
- Disable SSL and early TLS, and prefer TLS 1.2 or 1.3.
- Tested as
- Protocol configuration questions.
- Trap
- Leaving legacy versions enabled for compatibility.
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IPsec AH vs. ESP
AH provides integrity and authentication. ESP adds confidentiality through encryption.
- Remember
- Tunnel mode protects the whole original packet, while transport mode protects the payload.
- Tested as
- VPN questions.
- Trap
- Choosing AH when confidentiality is required.
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CRL vs. OCSP
A CRL is a published list of revoked certificates. OCSP checks a certificate's status in real time.
- Remember
- Both check revocation, and OCSP is more current.
- Tested as
- PKI operations.
- Trap
- Confusing revocation with expiry.
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Key escrow
A trusted party holds copies of keys for authorized recovery.
- Remember
- It enables recovery but must itself be strongly protected.
- Tested as
- Key management questions.
- Trap
- Escrowing signing keys, which undermines non-repudiation.
Side by side
Concepts candidates mix up, compared on the point that decides the answer.
Hashing vs. HMAC vs. digital signature vs. encryption
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Hashing | One-way digest of data | Integrity only, no key | Using it for confidentiality |
| HMAC | Hash combined with a shared secret key | Integrity and authenticity between key holders | Expecting non-repudiation |
| Digital signature | Hash signed with the sender's private key | Integrity, authenticity and non-repudiation | Thinking it provides confidentiality |
| Encryption | Reversible transformation with a key | Confidentiality | Assuming it proves who sent the data |
Symmetric vs. asymmetric encryption
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Symmetric | Same key encrypts and decrypts | Fast, but key distribution is hard | Sharing keys over insecure channels |
| Asymmetric | Public and private key pair | Solves key exchange and enables signatures, but is slower | Using it to encrypt large volumes of data |
PKI vs. web of trust
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| PKI | Certificate authorities vouch for identities | Central, hierarchical trust | Assuming any certificate is trustworthy without validation |
| Web of trust | Users vouch for each other's keys, as in PGP and GPG | Decentralized trust | Expecting central revocation |
Exam traps
Each trap is an answer that looks right. Learn the clue that should change your mind.
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HMAC for non-repudiation
- What candidates pick
- Use HMAC so the sender cannot deny sending a message.
- Why it looks right
- HMAC proves authenticity and integrity, and the outline lists it near non-repudiation.
- Why it's wrong
- Both parties share the key, so either could have created the code. A digital signature with a private key is needed.
Clue to watch for The requirement mentions proving origin to a third party or preventing denial.
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Encrypt the passwords
- What candidates pick
- Store passwords using AES encryption.
- Why it looks right
- AES is strong and widely approved.
- Why it's wrong
- Encrypted passwords can be decrypted if the key is stolen. Passwords should be stored as salted hashes using a slow hashing algorithm.
Clue to watch for The scenario is about storing credentials.
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Sign with the public key
- What candidates pick
- The sender signs a document with the recipient's public key.
- Why it looks right
- Public keys are used for encryption, which sounds similar.
- 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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DKIM for confidentiality
- What candidates pick
- Implement DKIM to keep email contents private.
- Why it looks right
- DKIM is a cryptographic email control.
- Why it's wrong
- DKIM signs messages to authenticate the sending domain and does not encrypt them.
Clue to watch for The requirement is confidentiality of message contents.
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AH for privacy
- What candidates pick
- Use IPsec AH to protect sensitive traffic from eavesdropping.
- Why it looks right
- AH is part of IPsec.
- Why it's wrong
- AH provides integrity and authentication only. ESP is needed for confidentiality.
Clue to watch for The requirement mentions eavesdropping or confidentiality.
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Wait for expiry
- What candidates pick
- Leave a compromised certificate in place until it expires next month.
- Why it looks right
- It will stop working soon anyway.
- Why it's wrong
- A compromised key must be revoked immediately so relying parties stop trusting it.
Clue to watch for The private key has been exposed or stolen.
Answer framework
For any Domain 5 scenario, use these steps to choose the right cryptographic answer.
- State the goal precisely, whether confidentiality, integrity, authenticity or non-repudiation, because each points to a different mechanism.
- Choose the mechanism that delivers that goal, such as hashing, HMAC, a digital signature, or symmetric or asymmetric encryption.
- Work out which key is used, remembering that the sender's private key signs and the recipient's public key encrypts for confidentiality.
- Check the protocol, version and mode against the use case, preferring TLS 1.2 or 1.3, ESP for confidentiality, and salted hashes for stored passwords.
- Consider the whole key life cycle, including generation with good entropy, protection, rotation, revocation on compromise, and secure destruction.
Practice question
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Study strategy
Despite its low weight, give this domain steady attention, because its concepts appear in network, access and endpoint questions too. Start with 5.2: build a table that maps each goal to its mechanism, then practice 'which key' questions until they are automatic.
Next, study password storage, salting and the common attacks, since these produce practical scenario questions. Make sure you can explain why HMAC does not provide true non-repudiation even though the outline lists it nearby.
Then cover secure protocols in 5.3 by use case. For each, ask what it protects and what it does not, for example DKIM authenticating senders without encrypting content. Finish with PKI and key management in 5.4, focusing on revocation and escrow. Candidates commonly underestimate entropy and the quantum topics in 5.1, which are short but explicitly listed.
Afterwards, move to Domain 6, where TLS, IPsec, VPNs and wireless encryption put these concepts into network practice.
FAQ
How much of the SSCP exam is Domain 5?
Cryptography carries 9% under the outline effective 1 October 2025, the smallest domain weight. Cryptographic concepts also appear in other domains.
Do I need to do cryptographic math?
No. Questions focus on choosing and applying mechanisms, keys and protocols correctly, not on calculations.
Does HMAC provide non-repudiation?
Not on its own. HMAC proves integrity and authenticity between parties sharing a key, but either party could have created it. Digital signatures provide non-repudiation.
Why salt password hashes?
A unique salt per password defeats precomputed rainbow tables and makes identical passwords produce different hashes.
Which key signs a message?
The sender's private key. Anyone can verify the signature with the sender's public key.
What about quantum computing?
The outline mentions quantum cryptography and quantum key distribution under entropy. Know that quantum computing threatens current public key algorithms and that post-quantum algorithms are being adopted.
How does Domain 5 relate to Domain 6?
Domain 6 applies cryptography in network protocols and wireless security, such as TLS, IPsec, VPNs and WPA3.
Other Cybersecurity certifications
Where the same subject shows up in other exams. Cards marked "Same subject" open the matching domain.
- Certified Ethical Hacker Same subject: Domain 9: Cryptography (5%)
- 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 5 knowledge
You have covered why cryptography is used, how its mechanisms work, secure protocols and PKI. Test whether you can match goals to mechanisms and keys under exam conditions.