Digital forensic investigation is the scientific process of collection, preservation, examination, analysis, documentation and presentation of digital evidence from digital devices, so that the evidence is in compliance with legal terms and acceptable in a court of law. Integrity of the digital evidence is an indispensable part of the investigation process and should be preserved to maintain the chain of custody. This is done through hashing technique using standardized forensic tools. However, while handling the evidences , lack of knowledge might lead to unintentional alteration of computed hash. This violates the chain of custody and makes the evidence inadmissible in a court of law. In this paper, our objective is to determine the different conditions under which the original hash value of a digital evidence changes. For this, we create different scenarios using sample data files and compute their hash values. A comparative study and analysis are done to determine in which scenario the original hash value of the data file changes. The results of the research will prove useful and essential for Criminal Justice Functionaries in gaining knowledge about various conditions leading to the change in hash value of digital evidence and therefore, avoid its accidental alteration during forensic investigation/examination.
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