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Insecure generation of random numbers - Static IV


Secure generation of random numbers and dynamic initialization vectors


  • Usage of Scala for functional and object-oriented programming in the JVM environment
  • Usage of javax.crypto for cryptographic operations in Java


Non compliant code

import javax.crypto.spec.IvParameterSpec

val staticIv = "1234567890123456" // Static, hardcoded IV
val iv = new IvParameterSpec(staticIv.getBytes)

In the above code, we are dealing with a vulnerability related to the insecure generation of random numbers. More specifically, the vulnerability is in the use of a static, hardcoded initialization vector (IV).

The IvParameterSpec class in Java's Cryptography Extension (JCE) is used to create an initialization vector. An initialization vector is an arbitrary number that can be used along with a secret key for data encryption. It is meant to randomize the data and as a result, the same plaintext encrypted with the same key (but different IVs) will not be the same.

In the given code, staticIv, a hardcoded string, is being used as the initialization vector. This is problematic because it means that the IV is predictable and doesn't change, which can potentially allow an attacker to reverse engineer the encryption.

The getBytes() method is called on staticIv to convert the hardcoded string into a byte array, which is then passed to the IvParameterSpec constructor to create the IV.

This is a serious security vulnerability because the purpose of an IV is to provide randomness. By hardcoding the IV, we are essentially removing this randomness, making the encryption predictable and susceptible to attacks.


  • Use a secure random number generator to generate a random IV.
  • Store the generated IV securely.
  • Ensure that the IV is unique for each encryption operation.
  • Pass the generated IV to the encryption algorithm.

Compliant code

import javax.crypto.spec.IvParameterSpec

val secureRandom = new SecureRandom()
val iv = new Array[Byte](16)
val ivSpec = new IvParameterSpec(iv)

The previous code was using a static, hardcoded initialization vector (IV) for encryption, which is a security vulnerability. An attacker who knows the IV can perform a reverse engineering attack to predict the random values that should remain secret.

The updated code uses the SecureRandom class from the package to generate a random IV. This class provides a cryptographically strong random number generator (RNG).

The SecureRandom instance is used to generate a byte array of length 16, which is the size needed for the IV. The nextBytes method is used to generate the random values and store them in the byte array.

The byte array is then passed to the IvParameterSpec constructor to create a new IV.

This ensures that the IV is unique for each encryption operation, which significantly increases the security of the encryption process. The generated IV should be stored securely and used for the corresponding decryption operation.