Pseudorandom Number Generator

A transaction that generates a pseudorandom number. When the pseudorandom number generate transaction executes, its transaction record will contain the 384-bit array of pseudorandom bytes. The transaction has an optional range parameter. If the parameter is given and is positive, then the record will contain a 32-bit pseudorandom integer r, where 0 <= r < range instead of containing the 384 pseudorandom bits.

When the nth transaction needs a pseudorandom number, it is given the running hash of all records up to and including the record for transaction n-3. If it needs 384 bits, then it uses the entire hash. If it needs 256 bits, it uses the first 256 bits of the hash. If it needs a random number r that is in the range 0 <= r < range, then it lets x be the first 32 bits of the hash (interpreted as a signed integer).

The choice of using the hash up to transaction n-3 rather than n-1 is to ensure the transactions can be processed quickly. Because the thread calculating the hash will have more time to complete it before it is needed. The use of n-3 rather than n-1000000 is to make it hard to predict the pseudorandom number in advance.\

Reference: HIP-351

Field	Description
Range	The specified range to return the pseudorandom number from.

Methods

Method	Type	Requirement
setRange(<range>)	integer	Optional
getRange(<range>)	integer	Optional

Java

//Create the transaction with range set
TransactionResponse transaction = new PrngTransaction()
        //Set the range
        .setRange(250)                
        .execute(client);

//Get the record
TransactionRecord transactionRecord = transaction.getRecord(client);

//Get the number
int prngNumber = transactionRecord.prngNumber;

System.out.println(prngNumber);

//SDK version 2.17.0

//Create the transaction with range set
const transaction = await new PrngTransaction()
        //Set the range
        .setRange(250)                
        .execute(client);

//Get the record
const transactionRecord = await transaction.getRecord(client);

//Get the number
const prngNumber = transactionRecord.prngNumber;

console.log(prngNumber);

//SDK version 2.17.0

transaction, err := hedera.NewPrngTransaction().
	// Set the range
	SetRange(250).
	Execute(client)
if err != nil {
	println(err.Error(), ": error executing rng transaction")
	return
}

transactionRecord, err := createResponse.GetRecord(client)
if err != nil {
	println(err.Error(), ": error getting receipt")
	return
}

if transactionRecord.PrngNumber != nil {
	println(err.Error(), ": error, pseudo-random number is nil")
	return
}

println("The pseudorandom number is:", *transactionRecord.PrngNumber)

//Version 2.17.0

// Create the transaction with range set
let transaction = PrngTransaction::new()
    .range(250)
    .execute(&client)
    .await?;

// Get the record
let record = transaction.get_record(&client)?;

// Get the number
if let Some(prng_number) = record.prng_number {
    println!("The pseudorandom number is: {:?}", prng_number);
} else {
    println!("No pseudorandom number returned in the record.");
}

// v2.17.0+