Java Community | Help. Code. Learn.•3w ago

I need something faster than BigInteger.probablePrime

i have an method:

    public SSPSharedPair createSharedPair() { // slow method
        Timer timer = new Timer() {{ this.run(); }};

        Random random = this.getRandom();
        System.out.println("random: "+timer.step().relative()+"ms");

        BigInteger generator = new BigInteger(String.valueOf(this.generatorInt()));
        System.out.println("generator: "+timer.step().relative()+"ms");

        BigInteger prime = BigInteger.probablePrime(this.bitLength(), random);
        System.out.println("prime: "+timer.step().relative()+"ms");

        SSPSharedPair sspSharedPair = new SSPSharedPair(generator, prime);
        System.out.println("pair: "+timer.step().relative()+"ms");
        
        return sspSharedPair;
    }

    public SSPSharedPair createSharedPair() { // slow method
        Timer timer = new Timer() {{ this.run(); }};

        Random random = this.getRandom();
        System.out.println("random: "+timer.step().relative()+"ms");

        BigInteger generator = new BigInteger(String.valueOf(this.generatorInt()));
        System.out.println("generator: "+timer.step().relative()+"ms");

        BigInteger prime = BigInteger.probablePrime(this.bitLength(), random);
        System.out.println("prime: "+timer.step().relative()+"ms");

        SSPSharedPair sspSharedPair = new SSPSharedPair(generator, prime);
        System.out.println("pair: "+timer.step().relative()+"ms");
        
        return sspSharedPair;
    }

the result of which:

random: 1ms
generator: 0ms
prime: 6621ms
pair: 0ms

random: 1ms
generator: 0ms
prime: 6621ms
pair: 0ms

this.bitLength() is always 2048 this.getRandom() is always new SecureRandom()

20 Replies

JavaBot•3w ago

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dan1st•3w ago

This is not a valid benchmark! If you want to create proper benchmarks, you should use JMH Java specifically optimizes code that is executed frequently

swimerOP•3w ago

Well, the problem is that it takes a long time to complete

dan1st•3w ago

otherwise you'll get wrong measurements it's slow initially but it gets faster when calling it often

swimerOP•3w ago

are there no more stable methods in java? im using jdk 21

dan1st•3w ago

What do you mean with stable?

swimerOP•3w ago

I want to generate a number as quickly as possible and ideally without the "slowly at first" conditions

dan1st•3w ago

CDS could help with that but it's a bit difficult to set up For testing: Can you try with Random instead of SecureRandom? I want to know whether the SecureRandom or the actual BigInteger.probablyPrime os tje ossie CDS can improve startup time by making stuff faster to load though I don't think it would do much for your BigInteger test (without the AOT cache)

swimerOP•3w ago

new Random() takes 1083ms ThreadLocalRandom.current() takes 608ms

dan1st•3w ago

and how long does the BigInteger.probablePrime take with those?

swimerOP•3w ago

it's probablePrime with them

dan1st•3w ago

then the issue is the random number generation Are you on Windows?

swimerOP•3w ago

the creation of an instance is performed once at startup, so it does not matter how long it takes to create a random yes exactly

dan1st•3w ago

you might be able to pick a default SecureRandom RNG

swimerOP•3w ago

I would like to generate a 2048 bit number, but it takes too long. I could roughly calculate how many bits 1 digit takes and generate it through for, but is it correct? I'm not sure that generating each number separately will be faster

dan1st•3w ago

there are different SecureRandom providers https://docs.oracle.com/en/java/javase/21/docs/specs/security/standard-names.html#securerandom-number-generation-algorithms Try the following:

SecureRandom.getInstance("NativePRNG")
SecureRandom.getInstance("NativePRNGBlocking")
SecureRandom.getInstance("NativePRNGNonBlocking")
SecureRandom.getInstance("PKCS11")
SecureRandom.getInstance("SHA1PRNG")
SecureRandom.getInstance("Windows-PRNG")

SecureRandom.getInstance("NativePRNG")
SecureRandom.getInstance("NativePRNGBlocking")
SecureRandom.getInstance("NativePRNGNonBlocking")
SecureRandom.getInstance("PKCS11")
SecureRandom.getInstance("SHA1PRNG")
SecureRandom.getInstance("Windows-PRNG")

or use Linux :p

swimerOP•3w ago

I'm just making a server that will be on Linux in the future Windows-PRNG - 3200ms SHA1PRNG - 1400ms PKCS11 - not available

dan1st•3w ago

and the others? 1400ms is pretty good

Madjosz•3w ago

Use https://www.random.org/

RANDOM.ORG - True Random Number Service

RANDOM.ORG offers true random numbers to anyone on the Internet. The randomness comes from atmospheric noise, which for many purposes is better than the pseudo-random number algorithms typically used in computer programs.

JavaBot•3w ago

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I need something faster than BigInteger.probablePrime

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