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20 - Cryptography

Module 20 - Cryptography

What is Cryptography?

Cryptography is the science and practice of securing communication and information by encoding it in a way that only authorized parties can access and understand. It involves the use of mathematical algorithms to transform plaintext (unencrypted information) into ciphertext (encrypted information) and vice versa. Cryptography plays a crucial role in ensuring the confidentiality, integrity, authenticity, and non-repudiation of data in various applications, including communication, data storage, and digital transactions.

Here are some key concepts and components of cryptography:

  1. Encryption: Encryption is the process of converting plaintext into ciphertext using a specific algorithm and a secret key. The encrypted data can only be deciphered (decrypted) by someone who possesses the corresponding decryption key.
  2. Decryption: Decryption is the reverse process of encryption, where ciphertext is transformed back into plaintext using the decryption key. Only authorized parties with the correct key can perform this operation.
  3. Key: A key is a secret or unique piece of information used to control the encryption and decryption processes. The strength of a cryptographic system often depends on the security of the key.
  4. Symmetric Cryptography: In symmetric-key cryptography, the same key is used for both encryption and decryption. Both the sender and the receiver must have access to this shared key.
  5. Asymmetric Cryptography: Asymmetric-key cryptography, also known as public-key cryptography, uses a pair of keys: a public key for encryption and a private key for decryption. Anyone can use the public key to encrypt data, but only the holder of the private key can decrypt it.
  6. Cryptographic Algorithms: These are mathematical procedures and formulas used to perform encryption and decryption. Examples include Advanced Encryption Standard (AES), RSA, and Elliptic Curve Cryptography (ECC).
  7. Hash Functions: Cryptographic hash functions take an input (message or data) and produce a fixed-size output called a hash value or digest. Hash functions are used for data integrity and digital signatures.
  8. Digital Signatures: Digital signatures use asymmetric cryptography to verify the authenticity and integrity of digital messages or documents. They provide a means of confirming that a message was sent by a specific person or entity.
  9. Cryptanalysis: Cryptanalysis is the science of studying and attempting to break cryptographic systems. It involves analyzing encrypted data to discover weaknesses and vulnerabilities in cryptographic algorithms.

Creating Self-Signed Certificate with Inetmgr

  • Open inetmgr
  • Click machine name and select Server Certificates
  • From actions select Create Self signed Certificate
  • Choose Name and Personal. Go to a Site, choose Bindings from the Action panel
  • Select Add
  • Select Https, IP 10.10.10.16, hostname www.goodshopping.com, select the certificate
  • Go the site and right click refresh one time.

Hash identifier

{% embed url="https://www.kali.org/tools/hashid/" %}

Find/Decrypt Hash Online

  • Hashes.com

{% embed url="https://hashes.com/en/decrypt/hash" %}

  • CrackStation.net

{% embed url="https://crackstation.net/" %}

  • CyberChef

{% embed url="https://gchq.github.io/CyberChef/" %}

Windows

Calculate Hash of text/File by HashCalc

{% content-ref url="../tools/hashcalc.md" %} hashcalc.md {% endcontent-ref %}

Calculate MD5 Hashes using MD5 Calculator

{% content-ref url="../tools/md5-calculator.md" %} md5-calculator.md {% endcontent-ref %}

Encode and Decode Text

Encode and Decode Text using BCTextEncoder

{% content-ref url="../tools/bctextencoder.md" %} bctextencoder.md {% endcontent-ref %}

Encode/Decode Text (File Extension is .hex) using CrypTool

  • File → New → Enter Text → Encrypt/Decrypt → Symmetric (Modern) → RC2 → KEY 05 → Encrypt
  • File → Open → Encrypt/Decrypt → Symmetric (Modern) → RC2 → KEY 05 → Decrypt

{% embed url="https://www.cryptool.org/en/" %}

Linux

Decrypt Hash using Hashcat

# In Parrot/Kali
hash-identifier #to identify the type of hash, its mode etc
hashid -m <hash> #alternative
 
hashcat -h

-a attack mode
-m hashtype
900 md4
1000 NTLM
1800 SHA512CRYPT
110 SHA1 with SALT HASH
0  MD5
100 SHA1
1400 SHA256
3200 BCRYPT
160 HMAC-SHA1
        
 #Decrypt Hashes
 hashcat '5f4dcc3b5aa765d61d8327deb882cf99' /usr/share/wordlists/rockyou.txt
 hashcat -a 3 -m 900 hash.txt /usr/share/wordlists/rockyou.txt

{% content-ref url="../tools/hashcat.md" %} hashcat.md {% endcontent-ref %}

Decrypt Hash using John the Ripper

  • First analyze hash type -> john hashfile.hash
  • Then crack hash -> john hashfile.hash --wordlist=/usr/share/wordlists/rockyou.txt --format=Raw-SHA1
  • Show the cracked password -> john --show --format=Raw-SHA1 hashfile.hash OR `john --show hashfile.hash

{% content-ref url="../tools/john-the-ripper.md" %} john-the-ripper.md {% endcontent-ref %}

Perform Disk Encryption using VeraCrypt

Create Encrypted containers which can be mounted as Virtual Disks.

Creation

  • Click VeraCrypt
  • Create Volumn
  • Create an encrypted file container
  • Specify a path and file name
  • Set password
  • Select NAT
  • Move the mouse randomly for some seconds, and click Format
  • Exit

Mount Volume

  • Select a drive, select file, open, mount
  • Input password
  • Dismount
  • Exit

{% embed url="https://www.veracrypt.fr/en/Beginner's%20Tutorial.html" %} VeraCrypt Step by step tutorial {% endembed %}

{% content-ref url="../tools/veracrypt.md" %} veracrypt.md {% endcontent-ref %}

Integrity Checking of file

Hashing is used for integrity checking. You can check if some file has been modified by comparing the hash values

Windows

  • Get-FileHash is the built-in PowerShell cmdlet that can be used to generate a hash value, allowing you to verify against the reference hash.
Get-FileHash <Location> -A SHA256 (SHA-1/256/384/512/MD5)
(Get-FileHash <Location> -A SHA256 ).hash -eq "<hash value>" #will return true or false

{% embed url="https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/get-filehash?view=powershell-7.3" %}

  • WinMD5Free: A simple and free utility that allows you to calculate and compare MD5 checksums in Windows. You can drag and drop files into the program to generate and compare checksums.
  • FCIV (Microsoft File Checksum Integrity Verifier): A command-line utility provided by Microsoft that allows you to compute and verify hash values for files. You can use it to create checksums and compare them.
  • HashMyFiles: A free utility from NirSoft that provides a graphical user interface for calculating and comparing file hashes. It allows you to compare the hashes of multiple files at once.
  • File Checksum Tool: A user-friendly tool that can calculate and compare checksums for various hash algorithms like MD5, SHA-1, and SHA-256. It provides an easy way to verify file integrity.

Linux

  • sha256sum (or md5sum, sha1sum): These are built-in Linux commands for calculating the hash (SHA-256, MD5, SHA-1) of a file. You can use them in the terminal to calculate and compare checksums.
  • GtkHash: A graphical tool for Linux that supports various hash algorithms and provides a user-friendly interface for calculating and comparing file hashes. It integrates well with the Linux desktop environment.
  • RapidCRC: While primarily designed for Windows, there is a Linux version available. It's a user-friendly tool that supports a variety of checksum algorithms and is particularly useful for comparing and verifying large sets of files.
  • Hashdeep: A command-line tool for hashing files in Linux and Windows. It can create hash sets for multiple files and directories, and it's useful for verifying file integrity.