CISSP · Domain 3
Security Architecture and Engineering
About 13% of the exam
Secure design principles
- Least privilege: only what the job needs
- Defense in depth: layered, independent controls
- Fail securely, deny when unsure
- Separation of duties splits critical tasks
- Complete mediation: check every access, every time
- Keep it simple, minimize attack surface
- Secure defaults out of the box
- Privacy by design and by default
- Shared responsibility: provider and customer both own parts
Security models
Confidentiality
- Bell-LaPadula
- no read up, no write down
- Simple security
- the no read up rule
- Star property
- the no write down rule
- Strong star
- read and write at own level only
- Strong tranquility
- labels never change while running
Integrity
- Biba
- no read down, no write up
- Invocation property
- cannot call a higher subject
- Clark-Wilson
- well-formed transactions via programs
- Access triple
- subject, program, object
- IVP and TP
- verify state, transform CDIs
Other models
- Brewer-Nash
- Chinese Wall, dynamic conflict of interest
- Graham-Denning
- eight rules for subjects and objects
- Harrison-Ruzzo-Ullman
- rights assignment, safety question
- Take-Grant
- take, grant, create, remove
- Lipner
- BLP plus Biba for commercial use
- Noninterference
- high actions invisible to low
BLP guards secrets by direction of flow; Biba is BLP flipped upside down; Clark-Wilson trusts the program, not the user
Trusted computing and evaluation
- TCB
- everything the security policy relies on
- Reference monitor
- concept that mediates all access
- Security kernel
- the reference monitor implemented
- Security perimeter
- boundary between TCB and the rest
- TPM
- chip for keys and boot measurements
- HSM
- tamper-resistant key generation and use
- Remote attestation
- prove platform state to a verifier
- Common Criteria
- PP, ST, TOE, assurance levels
EAL1 functionally tested, EAL4 methodically designed and reviewed, EAL7 formally verified: assurance, never a promise of zero bugs
Symmetric vs asymmetric
Symmetric
- One shared secret key
- Fast, bulk data encryption
- Key distribution is the hard part
- n users need n(n-1)/2 keys
- Block: AES, 3DES, Blowfish, Twofish
- Stream: ChaCha20, RC4 (broken)
- Modes: ECB weak, CBC, CTR, GCM authenticated
Asymmetric
- Public and private key pair
- Slow, used for keys and signatures
- Solves distribution, gives nonrepudiation
- n users need 2n keys
- RSA factoring, ECC discrete log on curves
- Diffie-Hellman agrees a key over open channel
- ECC: same strength, far smaller keys
Hybrid in practice
- Asymmetric wraps a symmetric session key
- TLS, S/MIME, PGP all work this way
- Ephemeral DH gives forward secrecy
- Post-quantum lattice schemes replace RSA and ECC
- Homomorphic: compute on data still encrypted
- One-time pad: random, message-length, never reused
Hashing, MAC and signatures
- Hash
- one-way fixed digest, integrity only
- Collision
- two inputs, same digest
- MD5, SHA-1
- deprecated, collisions exist
- SHA-256
- 256-bit digest, current standard
- HMAC
- hash plus shared secret key
- Digital signature
- hash encrypted with sender private key
- Signature gives
- integrity, authenticity, nonrepudiation
- Salt
- random value defeats rainbow tables
Sign with your private key, verify with the sender's public key; encrypt with the receiver's public key
PKI and key management
- CA issues and signs certificates
- RA verifies identity before issuance
- X.509 binds a public key to a name
- CRL lists revoked, OCSP checks live
- Certificate pinning resists rogue CAs
- Key escrow: third party holds copies
- Lifecycle: generate, distribute, store, rotate, revoke, destroy
- Kerckhoffs: only the key stays secret
- Split knowledge and dual control for master keys
Cryptanalytic attacks
- Brute force
- try every key, work factor
- Ciphertext only
- attacker holds only ciphertext
- Known plaintext
- pairs of plain and cipher
- Chosen plaintext
- attacker picks what gets encrypted
- Chosen ciphertext
- attacker picks what gets decrypted
- Birthday attack
- find collisions faster than expected
- Meet in the middle
- why double DES fails
- Side channel
- timing, power, emanation leaks
- Replay
- resend captured message, beat with nonces
- Frequency analysis
- breaks substitution ciphers
System and platform vulnerabilities
- Covert channels: storage or timing leaks
- TOCTOU race between check and use
- Buffer overflow overwrites adjacent memory
- Rogue hypervisor below the OS, VM escape
- Maintenance hooks and backdoors
- Emanations: TEMPEST shielding, white noise
- IoT: tiny memory, rare firmware updates
- ICS and SCADA: availability first, legacy protocols
- Cloud misconfiguration is the customer's fault
Cloud, virtualization, emerging
- IaaS, PaaS, SaaS
- customer controls less each step
- Type 1 hypervisor
- runs on bare metal
- Type 2 hypervisor
- runs on a host OS
- Containers
- share one kernel, isolate processes
- Serverless
- provider runs the code on demand
- Microservices
- small services, many trust boundaries
- Edge and fog
- compute near the data source
- Zero trust (800-207)
- policy engine decides, PEP enforces
- Cloud assurance registry
- self-assess, audit, continuous monitor
Site and facility design
- CPTED: design that discourages crime
- Concentric rings, layered zones inward
- Mantrap stops piggybacking and tailgating
- Data center away from exterior walls
- Wiring closets locked, media protected
- Positive pressure pushes contaminants out
- Hot and cold aisle containment
- Humidity 40 to 60 percent
- Water detection below raised floors
Fire and power
- Class A
- common combustibles, water or soda acid
- Class B
- liquids and gases, CO2 or foam
- Class C
- electrical, CO2 or clean agent
- Class D
- combustible metals, dry powder
- Class K
- kitchen oils, wet chemical
- Wet pipe
- water always in the pipe
- Dry pipe
- air until a head opens
- Preaction
- two triggers before water flows
- Fault, blackout
- brief, then prolonged loss
- Sag, brownout
- brief, then prolonged low voltage
- Spike, surge
- brief, then prolonged high voltage
Storage and RAID
- RAID 0
- striping, speed, no redundancy
- RAID 1
- mirroring, half the capacity
- RAID 5
- distributed parity, survives one drive
- RAID 6
- dual parity, survives two drives
- RAID 10
- mirror pairs then stripe
- Degraded array
- second RAID 5 failure loses everything
- SAN vs NAS
- block storage vs file shares
RAID protects availability against drive failure; it is not a backup and never protects against deletion or ransomware
Rapid recall: numbers
- AES
- 128-bit block, 128/192/256 keys
- DES
- 64-bit block, 56-bit key
- 3DES
- 112 bits effective, retired
- RSA
- 2048 bits minimum today
- ECC 256
- roughly RSA 3072 strength
- SHA-256
- 32-byte digest
- MD5
- 128-bit digest, broken
- TCSEC
- D, C1, C2, B1, B2, B3, A1
- ITSEC
- F function, E assurance ratings
Key formulas and rules
- Symmetric keys for n people: n(n-1)/2
- Asymmetric keys for n people: 2n
- Work factor: time and cost to break
- Confusion hides key, diffusion spreads change
- Avalanche: one bit flips half the output
- Nonrepudiation needs asymmetric signatures
- Authenticated encryption: confidentiality plus integrity together
Never roll your own crypto: choose vetted algorithms, protect the keys, and plan for algorithm retirement
Reference strip: names to recognize
Models
- Bell-LaPadula, Biba, Clark-Wilson
- Brewer-Nash, Graham-Denning, HRU
- Take-Grant, Lipner, Sutherland
- State machine, lattice, information flow
Evaluation and standards
- Common Criteria ISO 15408, EAL1 to EAL7
- TCSEC Orange Book, ITSEC Europe
- FIPS 140-3 crypto module levels 1 to 4
- NIST SP 800-207 zero trust
- ISO 27001 ISMS, ISO 27017 cloud
Algorithms
- AES, 3DES, Blowfish, Twofish, ChaCha20
- RSA, ECC, Diffie-Hellman, ElGamal, DSA
- SHA-2, SHA-3, HMAC, bcrypt, Argon2
- Post-quantum: ML-KEM, ML-DSA
Protocols and hardware
- TLS 1.3, IPsec, SSH, S/MIME, PGP
- TPM, HSM, secure enclave, smart card
- Secure boot and measured boot
- Kerberos symmetric, PKI asymmetric
Physical
- CPTED, concentric rings, mantrap
- Fire classes A, B, C, D, K
- Wet, dry, preaction, deluge sprinklers
- UPS, generator, surge protection
- Faraday cage, TEMPEST, white noise
Quick exam traps
- Trap: Biba stops subjects reading up
- Trap: Bell-LaPadula protects integrity
- Trap: A Type 2 hypervisor runs on bare metal
- Trap: Hashing gives confidentiality
- Trap: A digital signature is made with the receiver's public key
- Trap: A longer key always means a stronger algorithm
- Trap: RAID is a backup strategy
- Trap: EAL7 certifies that no vulnerabilities exist
cybercertprep.com · original revision sheet written from the public body of knowledge