CWE-1204: Generation of Weak Initialization Vector (IV)

What is Generation of Weak Initialization Vector (IV)?

• Overview: The vulnerability involves the use of Initialization Vectors (IVs) in cryptographic operations that are not sufficiently random or unique, compromising the security of the cryptographic process.

• Exploitation Methods:

• Attackers can predict or replicate weak IVs, leading to successful decryption of data.
• Common attack patterns include replay attacks and cryptanalysis that exploit recurring patterns in IVs.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data due to decryption.
• Potential cascading effects could involve further compromise of the entire cryptographic system.
• Business impact includes data breaches, loss of customer trust, and potential legal ramifications.

• Prevention Guidelines:

• Specific code-level fixes include using secure random number generators for IV creation.
• Security best practices involve ensuring IVs are both unique and unpredictable for each encryption session.
• Recommended tools and frameworks include cryptographic libraries that implement secure IV generation, such as OpenSSL or Bouncy Castle.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

Here's an improved version of the content, addressing the issues you mentioned:

import os
from Crypto.Cipher import AES

def encrypt_data(data, key):
    # Vulnerable: Using a static IV which is insecure
    iv = b'0000000000000000'  # Static IV
    cipher = AES.new(key, AES.MODE_CBC, iv)
    ciphertext = cipher.encrypt(data)
    return ciphertext

Explanation:

• The code above demonstrates a vulnerability where a static Initialization Vector (IV) is used for AES encryption. A static IV is predictable and can allow attackers to detect patterns in encrypted data, leading to attacks like replay attacks or ciphertext pattern analysis. This compromises data confidentiality.

How to fix Generation of Weak Initialization Vector (IV)?

To fix this vulnerability, the IV should be unique and unpredictable for each encryption operation. This can be achieved by generating a random IV using cryptographically secure random number generation methods. This ensures that the IV is different each time, making it harder for attackers to exploit patterns in the encrypted data.

Best Practices:

1. Use Secure Random Generators: Utilize libraries or functions that provide cryptographically secure random numbers.
2. Unique IV per Encryption: Ensure each encryption operation uses a new, random IV to prevent pattern recognition.
3. IV Transmission: Safely transmit the IV along with the ciphertext. The IV does not need to be secret, but it must be unique and unpredictable.

Fixed Code Example

import os
from Crypto.Cipher import AES

def encrypt_data(data, key):
    # Fixed: Generate a random IV for each encryption operation
    iv = os.urandom(16)  # Secure, random IV generation
    cipher = AES.new(key, AES.MODE_CBC, iv)
    ciphertext = cipher.encrypt(data)
    return iv + ciphertext  # Prepend IV to ciphertext for transmission

Explanation:

• Line 6: Uses os.urandom(16) to generate a secure, random 16-byte IV for each encryption operation, ensuring unpredictability and uniqueness.
• Line 9: Prepends the IV to the ciphertext when returning it. This allows the recipient to extract the IV for decryption, maintaining the integrity and confidentiality of the encryption process. This method ensures that each encryption operation has a unique IV, mitigating the vulnerability.

The improved content now includes proper syntax highlighting, correct line number formatting, realistic code examples, and thorough explanations of the vulnerability and its fix.