Cracking Passwords in Forensic Investigations - Scholarly ...

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1.0 BACKGROUND Chapter One INTRODUCTION The use of passwords for securing data is a common practice for computer users. Passwords are used as a security mechanism to protect the privacy and confidentiality of data on computers. Passwords are used for a variety of applications, for example for securing a person’s e-mail account, bank account, computer, or private data in files and spreadsheets. Password protection not only ensures authentication of the user accessing the data, but in many cases it also supports encryption for the entity that needs to be protected. Encryption ensures the privacy of data, such that only the legitimate user can have access to the information. Therefore, any illegitimate user who does not have the password is unable to have access to the encrypted information. Passwords have proved to be optimal for security. However, passwords can also be used by people with malicious intent. A malicious person may use passwords and encryption to protect incriminating information from the access of law enforcement agencies. If the law enforcement agencies or forensic investigators are not provided with the password, it may not be possible for them to gain important evidence. Such a situation could hamper justice, as the malicious person may not be prosecuted in a court of law without credible evidence. Therefore, in such situations law enforcement agencies need to resort to various means of password recovery in order to gain access to the encrypted information. One of the most common methods of overcoming password protection is password cracking (Casey, 2004). Password cracking can be done using a variety of tools and techniques, the most common of which is to use automated software to try various possible guesses until the correct password is found. Other techniques involve the use of brute-force cracking methods, rainbow tables, and also Markov chains (Marechal, 2008). Hence, in order to recover passwords, law enforcement agencies need to use a variety of password cracking tools and techniques. 1
1.1 PROBLEMS FOR DIGITAL FORENSIC INVESTIGATORS There exist a variety of problems for digital forensic investigators in the field of password cracking. One major problem is the speed of password cracking. Due to improvements in security, the amount of time it takes to crack passwords encrypted with the latest secure algorithms is increasing. Thus, as security improves and advances, the number of challenges for the digital forensic investigator also increases. Another problem in the field of password cracking is the ambiguity in estimating whether or not the correct password will be found. If the password is very difficult and the encryption algorithm in use is secure, it is not possible to assume that a password will definitely be cracked. Also, a measure of probability for determining the chances of finding a correct password does not exist, since the password being searched for is unknown. As just discussed, the two major problems in the field of password cracking are the decreasing speed of password cracking and the ambiguity of the outcome of the password cracking process. These two major problems are the cause of even more problems and challenges for the digital forensic investigator. Password cracking is slow for strong passwords and passwords that are encrypted with a strong algorithm. Due to such slow speeds, it takes a lot of time to crack those passwords. This in turn leads to an increase in the amount of time for the associated legal cases to be resolved. The slow speed of password cracking and thus legal resolution also causes an escalation in the costs involved. Also, the cost involved for resolving the legal case becomes very high due to the large amount of time required. It is therefore a challenge to manage the time and also costs for password recovery. There are also other challenges for the digital forensic investigator. If the information to be accessed is in encrypted form, it is difficult to know whether or not the information is relevant to the investigation. Therefore, it is challenging to identify relevant information without cracking the password. Depending on the case, the digital forensic investigator may also have other challenges with regards to accessing the evidence. There may be social engineering challenges— for example, social engineering the suspect to allow an investigator to stealthily steal the password or gain clues to get the password. There may also be technical 2
Page 1 and 2: Cracking Passwords in Forensic Inve
Page 3 and 4: iii Acknowledgements This thesis wa
Page 5 and 6: v Abstract Digital Forensic Investi
Page 7 and 8: vii Table of Contents Declaration .
Page 9 and 10: ix Chapter 4 - Research Findings 4.
Page 11 and 12: xi List of Tables Table 2.1: The Mo
Page 13: xiii List of Abbreviations AMD Adva
Page 17 and 18: approach improves the password crac
Page 19 and 20: technologies, there exist challenge
Page 21 and 22: 2.1 PASSWORDS AND PASSWORD RECOVERY
Page 23 and 24: 2.1.2 Unix/Linux MD5 Password Schem
Page 25 and 26: encrypting the information within s
Page 27 and 28: iii) If possible, create a custom d
Page 29 and 30: Since all possible permutations and
Page 31 and 32: L0phtCrack 6 supports the retrieval
Page 33 and 34: i) Decryption attack: As discussed
Page 35 and 36: Full cost refers to the total amoun
Page 37 and 38: As shown in Table 2.3, a password w
Page 39 and 40: 5) Weir, Aggarwal, Medeiros, and Gl
Page 41 and 42: the speed of cracking and the attac
Page 43 and 44: is inevitable) but rather the optim
Page 45 and 46: Klein (1990) addressed the most com
Page 47 and 48: character hashing. Thus, for passwo
Page 49 and 50: experiments were conducted by gener
Page 51 and 52: obtained via phishing attacks on th
Page 53 and 54: Bengtsson (2007) outlined a literat
Page 55 and 56: applications whose passwords need t
Page 57 and 58: equired for computing and testing.
Page 59 and 60: 3.2.3 The Research Questions and Hy
Page 61 and 62: main experiment, which is the next
Page 63 and 64: 12,500 x 8 = 100,000 passwords/seco
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3.3.5 Data Map Figure 3.2: Research
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4.0 INTRODUCTION Chapter 4 Research
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4.1.2 Time Budgeting The time budge
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Another computer with the same conf
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minutes, and 24.8 days respectively
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vishal@vishal-desktop:~$ sudo addus
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Table 4.4: Monitoring/action-perfor
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4.3 ANALYSIS OF DATA The experiment
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Table 4.6: First 10 accounts’ pas
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DD:HH:MM:SS format, similar to the
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4.4 PRESENTATION OF DATA FINDING Af
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Figure 4.8 shows the time taken for
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Figure 4.11 displays the comparison
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5.0 INTRODUCTION Chapter 5 Research
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Thus, the simulation mirrored the f
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Table 5.1: Testing hypothesis H0 Hy
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Table 5.3: Testing hypothesis H2 Hy
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Q3: What are the guidelines for bes
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Since the passwords were arranged i
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Analysis (see Section 3.2.3). All f
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information for forensic investigat
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5.3.1.2 Second Step - Find Password
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Therefore, T (in seconds) = 12,500,
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6.0 RESEARCH SUMMARY Chapter 6 Conc
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udgets, the passwords were added to
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SECONDARY RESEARCH QUESTION 3: What
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overcome the security barriers of p
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Clayton, R., & Bond, M. (2003). Exp
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Openwall Project. (2010). John the
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APPENDIX 1: Time Budget Calculation
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51 Bas -2-38 TOTAL TIME REQUIRED FO
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96 Bas -2-27 97 Bas -2-28 98 Bas -2
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140 Adv -1-26 141 Bas -3-07 142 Adv
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182 Adv -1-21 183 Adv -1-22 Diction
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main12:$1$CSD0Tppt$0gO4c883evmn9sQR
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main41.txt: main41:$1$B43.jKTn$5EPi
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main70.txt: main70:$1$7kHK0PnH$yJ5x
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main99:$1$UQiTB..u$SJUkwarkM1kzvnvt
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main128.txt: main128:$1$n7OEbAyB$d6
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main157.txt: main157:$1$VRmaYxPu$Iy
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main186:$1$HFNaeUkb$t1lZ5QcrH9iy8G/
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SHA 1: a168282ad70a94fbb8d5917f3505
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C:\Main Test\MainTest-passwdFiles\B
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Job Started: 7/13/10 8:49:24 File M
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File Modified: 7/13/10 6:58:08 SHA
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File Version: Unknown Job Started:
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SHA 1: b95b12e95c70b66df01af148502e
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File Size: 60 File Version: Unknown
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Job Status: Finished on 7/13/10 8:5
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Identified Type: *nix passwd File S
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Password Type: Password Where Found
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Job Status: Finished on 7/13/10 10:
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MD5: df7c66c8b6b8528176d42314926021
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Result: trapezoidal@ Description: U
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Where Found: (ADV-1-20) Dictionary
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Password Type: Password Where Found
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Where Found: (BAS-3-04) Dictionary
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Commonly Registered Type: crypt use
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Where Found: --- C:\Main Test\MainT
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MD5: 17632fca93fa27bb8d0a89c80a2ba9
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Description: Unknown Password Type:
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File Version: Unknown Job Started:
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APPENDIX 4: Time Analysis for all B
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main60 main61 main62 main63 main64
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main127 main128 main129 main130 mai
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main192 main193 main194 main195 mai
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