SHA1PRNG解释

I find out that they are so less infomation abount sha1prng.

https://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html

oragle explain that :
SHA1PRNG

The name of the pseudo-random number generation (PRNG) algorithm supplied by the SUN provider. This algorithm uses SHA-1 as the foundation of the PRNG. It computes the SHA-1 hash over a true-random seed value concatenated with a 64-bit counter which is incremented by 1 for each operation. From the 160-bit SHA-1 output, only 64 bits are used.