Encryption at Rest, in Transit, in Use, and Key Management

CompTIA Security+ SY0-701

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1 Introduction & Exam Overview

Current Exam Facts and How Security+ Tests Judgment Domain Weighting and an 8-12 Week Study Plan Practice Questions, PBQs, and the Missed-Question Notebook

2 Domain 1: General Security Concepts (12%)

CIA and Non-Repudiation Control Types and Categories with Scenario Classification Security Principles: Least Privilege, Defense in Depth, Secure by Design, and Zero Trust Change Management and Business Impact

3 Domain 1: Identity, Trust, and Cryptography Basics

AAA and IAM Concepts Authentication Factors and MFA Traps Authorization Models: RBAC, ABAC, MAC, DAC, and Least Privilege Cryptography, Hashes, Signatures, PKI, and Certificate Decision Rules

4 Domain 2: Threat Actors, Vectors, and Social Engineering

Threat Actors and Motivations Attack Vectors and Attack Surface Social Engineering Types and Clues Supply Chain and Insider Threat Scenarios

5 Domain 2: Threats, Vulnerabilities, and Mitigations - Attacks

Malware Behaviors and Indicators Credential and Password Attacks Network and Wireless Attacks Application, API, and Cloud Attacks with Mitigation Mapping

6 Domain 2: Threats, Vulnerabilities, and Mitigations - Vulnerabilities

Vulnerability Types and Misconfiguration Vulnerability Scanning and Prioritization Secure Coding and Application Mitigations Remediation, Compensating Controls, and Risk-Based Decisions

7 Domain 3: Security Architecture - Secure Architecture Models

Architecture Models and Trust Boundaries Cloud Shared Responsibility and Service Models Zero Trust, SASE, and SSE Concepts Secure Design Review Scenarios

8 Domain 3: Security Architecture - Network Security Architecture

Segmentation, VLANs, DMZ, and Microsegmentation Firewalls, WAF, IDS, IPS, and Proxies VPN, Remote Access, and NAC Wireless Security and Enterprise Network Design

9 Domain 3 Part C: Data Protection and Resilience

Data Classification and Handling Encryption at Rest, in Transit, in Use, and Key Management DLP, Privacy, and the Data Lifecycle Backups, RTO, RPO, BCP, DR, and Resilience

10 Domain 4 Part A: Secure Operations for Hosts, Cloud, Mobile, and IoT

Endpoint and Server Hardening Cloud, Container, and Virtualization Operations Mobile, BYOD, and MDM Embedded, IoT, OT, and Physical Device Security

11 IAM Operations and Access Control

Provisioning, Deprovisioning, and Access Reviews PAM, JIT, JEA, and Service Accounts Federation, SSO, SAML, OIDC, and OAuth Account Attacks and IAM Monitoring

12 Logging, Monitoring, and Detection

Log Sources and Telemetry SIEM Correlation and Alert Triage SOAR, Playbooks, and Automation Detection Use Cases and False-Positive Handling

13 Incident Response

IR Phases and Roles Containment, Eradication, and Recovery Decisions Communication, Escalation, Legal, and Regulatory Considerations Post-Incident Lessons Learned and Metrics

14 Digital Forensics and Investigation

Evidence Handling and Chain of Custody Disk, Memory, Network, and Log Artifacts Order of Volatility and Acquisition Choices Forensic Reporting and Anti-Forensics Traps

15 Vulnerability, Patch, Asset, and Automation Operations

Asset Inventory and Data Classification in Ops Vulnerability Lifecycle and CVSS/Risk Priority Patch, Change, and Configuration Management Automation, Orchestration, SCAP, and Security Tooling

16 Governance, Policies, and Risk Management

Governance Documents: Policy, Standard, Procedure, and Baseline Risk Register and Risk Treatment Quantitative/Qualitative Risk and BIA Exceptions, Acceptance, Ownership, and Reporting

17 Third-Party Risk, Compliance, and Privacy

Vendor Risk Lifecycle and Agreements Due Diligence, Questionnaires, and Monitoring Privacy Concepts and Data Rights Compliance Reporting and Consequences

18 Audits, Penetration Testing, and Awareness

Internal and External Audits and Evidence Penetration Test Types and Rules of Engagement Security Awareness, Training, and Phishing Metrics Personnel and Physical Security Program Controls

19 Final Review and PBQ Labs

PBQ Workflow and Timing Ports, Protocols, and Acronyms High-Yield Tables Firewall, IAM, Log, and Risk PBQ Mini-Labs Final 7-Day Review Plan Mixed Exam Strategy and Missed-Question Remediation

Encryption at Rest, in Transit, in Use, and Key Management

Key Takeaways Explain This Topic AI

Encryption at rest protects stored data; in transit protects data moving across networks; in use protects data during processing.

Symmetric ciphers like AES-256 give fast bulk confidentiality; asymmetric pairs like RSA-2048/ECC handle key exchange, signatures, and identity.

Hashing (SHA-256) provides integrity only and is one-way; it is not encryption and is not reversible.

Key management usually matters more than algorithm choice on the exam: rotation, escrow, HSM/KMS storage, separation of duties.

A leaked, reused, or co-located key defeats an otherwise strong cipher, so keys must be stored apart from the data.

Last updated: June 2026

Encryption by Data State

Encryption transforms readable plaintext into ciphertext that is useless without the correct key, protecting confidentiality. Security+ SY0-701 Objective 3.3 wants you to identify where encryption is needed (the data state) and how the keys are protected .

Data state Meaning Example controls

At rest Stored on disk, database, object storage, backup, or device Full disk encryption (BitLocker, FileVault), database/column encryption, transparent data encryption

• In transit Moving across a network TLS 1.3, HTTPS, IPsec VPN, SSH, SFTP
• In use Being processed in CPU/RAM Trusted execution environment (TEE), secure enclave, confidential computing

Think stolen laptop or exposed storage bucket for at rest ; interception, downgrade, or man-in-the-middle for in transit ; and protecting a workload while it is actively decrypted in memory for in use .

Symmetric vs Asymmetric

• Property Symmetric Asymmetric
• Keys One shared secret Public/private key pair
• Speed Fast — used for bulk data Slow — used for small payloads
• Examples AES-128/256 , ChaCha20 RSA-2048 , ECC, Diffie-Hellman
• Main use Encrypting files, disks, sessions Key exchange, signatures, certificates

Real systems combine both: TLS uses asymmetric keys to exchange a symmetric session key, then encrypts the bulk traffic with AES. Knowing that hybrid model answers many stems.

Hashing, Salting, and Signatures

A hash (SHA-256, SHA-3) is a one-way digest used for integrity; identical input always yields identical output, but you cannot reverse it. A salt is a unique random value added before hashing a password to defeat precomputed rainbow tables. Key stretching (bcrypt, PBKDF2, Argon2) deliberately slows hashing to resist brute force. A digital signature hashes a message then encrypts the digest with the sender's private key, giving integrity, authenticity, and non-repudiation at once.

The verifier decrypts the signature with the sender's public key and re-hashes the message; if the digests match, the content is unaltered and provably came from the private-key holder.

Watch the directionality trap. For confidentiality you encrypt with the recipient's public key (only their private key decrypts). For a signature you encrypt the digest with your own private key (anyone with your public key verifies). Reversing those is the single most common cryptography mistake on the exam.

PKI and Certificates

A certificate binds a public key to an identity and is issued by a Certificate Authority (CA) . The chain runs root CA → intermediate CA → leaf certificate; clients trust the root and validate the chain. Revoked certificates appear on a Certificate Revocation List (CRL) or are checked in real time via Online Certificate Status Protocol (OCSP) , often with OCSP stapling so the server presents a signed status. A wildcard certificate ( *.example.com ) covers all first-level subdomains; a SAN certificate lists multiple specific names.

Key Management Concepts

• Concept Why it matters
• KMS Central service to generate, store, rotate, and audit keys
• HSM Tamper-resistant hardware that protects high-value keys and performs crypto operations
• TPM On-board chip storing platform keys, enabling full disk encryption and secure boot
• Key rotation Limits the exposure window if a key is compromised
• Key escrow Stores recovery keys under controlled access for continuity or legal need
• Key destruction Crypto-shredding renders ciphertext permanently unrecoverable
• Separation of duties / M-of-N No single person controls full key lifecycle or recovery
• Worked Scenario

A finance app stores payment records in a database and exports nightly backups to cloud object storage; users reach it through a web portal. The layered answer:

• Location Correct control
• Web connection TLS 1.3 with a valid, unexpired certificate
• Database Encryption at rest with access-controlled keys
• Backup objects Separate backup keys, restricted access
• Admin access MFA, logging, just-in-time elevation
• Key storage HSM- or KMS-backed, never hardcoded in source
• Common Exam Traps

"Hashing encrypts data" — hashing is one-way integrity, not reversible encryption.

"Share the private key with a partner" — share public keys; private keys never leave control.

"TLS protects data after it reaches the server" — TLS protects transit only; once decrypted at the endpoint you need at-rest and in-use controls.

"A strong algorithm makes hardcoded keys safe" — key exposure defeats any cipher.

Quick Drill

Protect a stolen laptop → encryption at rest (FDE/TPM).

Protect an API call over the internet → TLS in transit.

Prove a publisher signed an installer → digital signature.

Store root keys tamper-resistant → HSM.

Make records unrecoverable without wiping disks → destroy the key (crypto-shredding).

Cipher Modes and Common Pitfalls

Block ciphers like AES need a mode of operation . ECB encrypts each block independently and leaks patterns, so it is the textbook "wrong" choice; CBC , CTR , and GCM are preferred. GCM (Galois/Counter Mode) is widely tested because it provides authenticated encryption — confidentiality plus integrity in one step — which is why TLS 1.3 mandates AEAD ciphers such as AES-GCM and ChaCha20-Poly1305.

Perfect forward secrecy , achieved with ephemeral Diffie-Hellman (DHE/ECDHE), ensures that compromising a server's long-term key does not let an attacker decrypt past captured sessions, because each session used a unique, discarded key.