“The Early Random PRNG in iOS 7 is surprisingly weak,” said Tarjei Mandt senior security researcher at Azimuth Security. “The one in iOS 6 is better because this one is deterministic and trivial to brute force.”
The Early Random PRNG is important to securing the mitigations used by the iOS kernel.
“All the mitigations deployed by the iOS kernel essentially depend on the robustness of the Early Random PRNG,” Mandt said. “It must provide sufficient entropy and non-predictable output.”"