From 6824acbb68dd8a6b36d8a6fc6a4c8a922e8f5d21 Mon Sep 17 00:00:00 2001
From: NikVolf <nikvolf@gmail.com>
Date: Mon, 18 Mar 2019 17:06:00 +0100
Subject: [PATCH] add source for externsion field algo

---
 crypto/src/pghr13.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/src/pghr13.rs b/crypto/src/pghr13.rs
index 5fd8bd41..e587118a 100644
--- a/crypto/src/pghr13.rs
+++ b/crypto/src/pghr13.rs
@@ -98,6 +98,8 @@ fn fq_sqrt(a: Fq) -> Option<Fq> {
 	}
 }
 
+// Algorithm 9 Square root computation over Fq2, with q ≡ 3 (mod 4)
+// from https://eprint.iacr.org/2012/685.pdf (Square root computation over even extension fields)
 fn fq2_sqrt(a: Fq2) -> Option<Fq2> {
 	let a1 = a.pow(FQ_MINUS3_DIV4.into_u256());
 	let a1a = a1 * a;