window.crypto is used as the cryptographically strong source of pseudo random integers that serve as indices to memorable wordlist provided to your device. The passphrase generation is conducted on your device. Please use this application only if you believe that you do not have malware on your device.
|S| = P(2**16, n), where S is the search space and n is the desired passphrase length. For n=4, |S| > 1.8E19, acceptable in 2019. Adjust n (number of dreidel rows), according to your passphrase complexity needs.
As an interesting side note, please do not spin physical dreidels in real life (or coins, for that matter) to obtain random numbers. Spinning is a poor randomization process, since it amplifies the minute density differentials of the spinning object. This means that the nature of every dreidel game depends on the dreidel used.