Use crypto.randomBytes instead of Math.random;

[alexandr-mochalov-moc]

During the security scan, the AppSec platform has found a vulnerability in the library code and recommends to use cryptographic random instead of Math.ramdon. So there are changes according to these recommendations;

[coveralls]

Coverage remained the same at 100.0% when pulling ef2d0644950172b1becf36f2af117d740c189144 on AlexandrMochalov:master into a1bc3f838093e3b65a3c886dd9a061e3b98bd49c on crypto-utils:master.