SY0-701 General Security Concepts Practice Question
A legal team must send a confidential contract to a partner so only the intended recipient can read it, and the partner also needs assurance the file really came from your company. Which approach best meets both needs?
⚠ Common exam trap
Many exam-takers confuse hashing with encryption or think that password-protecting a zip file provides strong security and sender authentication, when in fact only a proper public-key infrastructure (PKI) with encryption and digital signatures meets both confidentiality and non-repudiation requirements.
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
✓
Encrypt the file with the recipient's public key and sign it with the sender's private key.
It uses asymmetric encryption to ensure confidentiality (encrypting with the recipient's public key ensures only the intended recipient can decrypt it with their private key) and digital signing (signing with the sender's private key provides non-repudiation and authenticity, proving the file came from the sender). This combination directly addresses both requirements: only the partner can read the contract, and the partner can verify the sender's identity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Hash the contract and email the hash value separately.
Why it's wrong here
Hashing the contract and emailing the hash value separately only provides integrity, not confidentiality or authenticity. The original contract is still sent in plaintext, so anyone who intercepts the email can read it. Additionally, a hash alone does not prove the sender's identity, as any party with the file can compute the same hash, and an attacker who replaces both the contract and the hash would go undetected.
- ✓
Encrypt the file with the recipient's public key and sign it with the sender's private key.
Why this is correct
Using the recipient's public key ensures only the intended recipient can decrypt the file, which provides confidentiality. Adding a digital signature with the sender's private key gives the partner a way to verify the file came from your company and has not been altered. Together, these controls address both privacy and authenticity, which is exactly what the scenario requires.
- ✗
Use a shared symmetric key and send the key in the same email message.
Why it's wrong here
Using a shared symmetric key to encrypt the file is algorithmically sound, but sending the key in the same email message completely defeats the encryption. Any attacker who intercepts the email gains both the ciphertext and the key, allowing them to decrypt the file with no additional effort. This also provides no authentication, as the sender's identity is not verified through public-key cryptographic signatures.
- ✗
Compress the file and password-protect the archive with a simple passphrase.
Why it's wrong here
Compressing the file and applying a simple passphrase with archive software relies on password-based encryption, which is typically weaker than public-key cryptography and is highly vulnerable to brute-force or dictionary attacks if the passphrase is simple. Furthermore, the passphrase would likely be transmitted via a separate email or message, creating a similar key-distribution vulnerability, and it offers no cryptographic proof of the sender's identity or the file's origin.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
Go deeper
Related to this question
Learn chapter
PKI and Digital Certificates
Key term
Asymmetric encryption
Asymmetric encryption is a cryptographic method that uses a pair of keys—a public key for encryption and a private key for decryption—to securely exchange data without sharing a secret.
Key term
Encryption
Encryption is the process of converting readable data into a secret code to prevent unauthorized access.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SY0-701 practice question is part of Courseiva's free CompTIA 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 SY0-701 exam.