Use of Cryptographically Weak Pseudo-Random Number Generator SHA1PRNG
This rule identifies instances where the Java SecureRandom class is instantiated with the SHA1PRNG algorithm. While SHA1PRNG has been widely used, it is considered less secure and potentially vulnerable compared to newer algorithms available. The use of stronger algorithms is recommended to ensure the cryptographic strength of random numbers.
The SHA1PRNG algorithm for SecureRandom may not provide a sufficiently strong
level of randomness for security-sensitive applications. SHA-1 has been
found to be weaker against collision attacks, and while SHA1PRNG is not
directly equivalent to SHA-1, its association and the lack of transparency
in its implementation across different Java platforms raise concerns about
its suitability and security. Modern cryptographic applications require
stronger guarantees of randomness to prevent attacks.
Example
import java.security.*;
public class WeakRNG {
public static void main(String[] args) {
try {
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
System.err.println("SHA1PRNG random algorithm not available.");
}
}
}
Remediation
It is recommended to use SecureRandom without specifying an algorithm,
allowing the Java runtime to select the strongest available algorithm, or
explicitly specify a more secure algorithm like NativePRNG or DRBG where
available and appropriate for the application's requirements. This ensures
the use of secure and up-to-date algorithms for random number generation.
import java.security.*;
public class StrongRNG {
public static void main(String[] args) {
SecureRandom sr = new SecureRandom();
}
}
False Positives
In the case of a false positive the rule can be suppressed. Simply add a
trailing or preceding comment line with either the rule ID (JAV004) or
rule category name (weak_prng).
- Using rule ID
- Using category name
import java.security.*;
public class WeakRNG {
public static void main(String[] args) {
try {
// suppress: JAV004
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
System.err.println("SHA1PRNG random algorithm not available.");
}
}
}
import java.security.*;
public class WeakRNG {
public static void main(String[] args) {
try {
// suppress: weak_prng
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
System.err.println("SHA1PRNG random algorithm not available.");
}
}
}