From 5c73e593c718ab2ddeba8fb1108153c8007f27b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lucas=20Men=C3=A9ndez?= <hi@lucasmenendez.me>
Date: Mon, 18 Nov 2024 09:17:54 +0100
Subject: [PATCH] fixing endianess issues

---
 ff.go   | 22 ++++++++++++++++++++++
 hash.go |  4 ++--
 2 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 ff.go

diff --git a/ff.go b/ff.go
new file mode 100644
index 0000000..444e985
--- /dev/null
+++ b/ff.go
@@ -0,0 +1,22 @@
+package arbo
+
+import "math/big"
+
+var (
+	// BN254BaseField is the base field for the BN254 curve.
+	BN254BaseField, _ = new(big.Int).SetString("21888242871839275222246405745257275088548364400416034343698204186575808495617", 10)
+	// BLS12377BaseField is the base field for the BLS12377 curve.
+	BLS12377BaseField, _ = new(big.Int).SetString("25825498262808887005865186224201665565126143020923472090132963926938185026661", 10)
+)
+
+// BigToFF function returns the finite field representation of the big.Int
+// provided. It uses the curve scalar field to represent the provided number.
+func BigToFF(baseField, iv *big.Int) *big.Int {
+	z := big.NewInt(0)
+	if c := iv.Cmp(baseField); c == 0 {
+		return z
+	} else if c != 1 && iv.Cmp(z) != -1 {
+		return iv
+	}
+	return z.Mod(iv, baseField)
+}
diff --git a/hash.go b/hash.go
index ae498cc..3584d5f 100644
--- a/hash.go
+++ b/hash.go
@@ -144,9 +144,9 @@ func (f HashMiMC_BLS12_377) Len() int {
 func (f HashMiMC_BLS12_377) Hash(b ...[]byte) ([]byte, error) {
 	h := mimc.NewMiMC()
 	for i := 0; i < len(b); i++ {
-		if _, err := h.Write(b[i]); err != nil {
+		if _, err := h.Write(SwapEndianness(b[i])); err != nil {
 			return nil, err
 		}
 	}
-	return h.Sum(nil), nil
+	return SwapEndianness(h.Sum(nil)), nil
 }