Option C is the best answer because CHFI v11 strongly emphasizes preserving original evidence , following data acquisition methodology , creating proper forensic duplicates, and maintaining chain of custody and best practices for handling digital evidence . It also includes validating data acquisition and legal concepts such as rules of evidence and evidence admissibility.

When dealing with encrypted hard drives, the correct forensic approach is first to create bit-by-bit copies and then perform all decryption attempts, cracking, or examination on the copies. This protects the original media from alteration, preserves the evidentiary record, and aligns with the best evidence principle by ensuring the originals remain intact and available for later verification or courtroom scrutiny.

Option A may be part of later analysis, but not on the original media. Option B introduces unnecessary exposure and evidentiary risk. Option D would destroy evidence. Therefore, the most defensible and CHFI-aligned method is to image the encrypted drives first and work only from the forensic copies , leaving the originals untouched.

This question aligns with CHFI v11 objectives under Operating System Forensics and File Type and Encoding Analysis . In digital forensics, file signature analysis—also known as magic number analysis —is a critical technique used to identify the true file type regardless of its extension. Attackers often rename or disguise files to evade detection, making hex-level inspection essential during forensic examinations.

Each file format begins with a unique hexadecimal header that identifies its structure. The hex value “89 50 4E 47” corresponds to the ASCII representation of ‰PNG , which is the standard file signature for Portable Network Graphics (PNG) files. CHFI v11 specifically emphasizes the use of hex editors to analyze file headers and detect file extension mismatches during investigations.

The other options have different signatures: PDF files start with 25 50 44 46 (%PDF) , JPEG files typically begin with FF D8 FF , and BMP files start with 42 4D (BM) . Since the observed hex value matches the PNG signature, the correct identification is PNG. This technique is vital for uncovering hidden or obfuscated evidence and ensuring accurate file classification in forensic investigations.