GPEN Attacking Password Hashes Practice Question
A penetration tester is performing an offline attack against a Kerberos TGS-REP hash obtained via Kerberoasting. Which of the following Hashcat modes should be used?
⚠ Common exam trap
Many exam-takers confuse Kerberoasting with AS-REP Roasting or assuming all Kerberos hashes use the same mode, but TGS-REP and AS-REP have distinct modes.
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
✓
13100
Kerberoasting produces a Kerberos 5 TGS-REP hash, typically using RC4 (etype 23). Hashcat mode 13100 is designed for this hash type. Other modes correspond to different Kerberos or NTLM hashes: 19600 for AES TGS-REP, 7500 for AS-REP, and 1000 for NTLM. Using the correct mode is essential for efficient cracking.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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19600
Why it's wrong here
Mode 19600 is for Kerberos 5 TGS-REP etype 17 (AES-128) hashes. Kerberoasting typically targets RC4 (etype 23) because it is weaker and more common, but if the service account uses AES, the hash would be etype 17. In this scenario, the tester obtained a TGS-REP hash via Kerberoasting, which is usually etype 23 unless specified otherwise. Without indication of AES, mode 13100 is correct.
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7500
Why it's wrong here
Mode 7500 is for Kerberos 5 AS-REQ Pre-Auth etype 23 hashes, which are used in AS-REP Roasting attacks. AS-REP Roasting targets accounts with pre-authentication disabled, yielding a different hash type. Kerberoasting targets service accounts with SPNs, resulting in TGS-REP hashes. Therefore, mode 7500 is incorrect for this scenario.
- ✓
13100
Why this is correct
Hashcat mode 13100 is specifically for Kerberos 5 TGS-REP etype 23 hashes, which are obtained through Kerberoasting. This mode implements the RC4-HMAC-MD5 algorithm used in etype 23. Using mode 13100 ensures Hashcat correctly parses the TGS-REP hash and performs the appropriate cracking operations, which involve decrypting the ticket with candidate passwords.
- ✗
1000
Why it's wrong here
Mode 1000 is for NTLM hashes, which are stored password hashes, not Kerberos tickets. Kerberoasting yields a TGS-REP hash that is encrypted with the service account's NTLM hash, but the hash format is specific to Kerberos. Using mode 1000 would not correctly parse the TGS-REP hash and would fail to crack it. The correct mode must match the Kerberos hash type.
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 |
About these practice questions
This GPEN question is part of Courseiva's 298-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official GIAC exam blueprint
This GPEN practice question is part of Courseiva's free GIAC 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 GPEN exam.