diff --git a/ecc/bls12-377/ecdsa/ecdsa.go b/ecc/bls12-377/ecdsa/ecdsa.go
index 288a9735f..d0ca34501 100644
--- a/ecc/bls12-377/ecdsa/ecdsa.go
+++ b/ecc/bls12-377/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bls12-378/ecdsa/ecdsa.go b/ecc/bls12-378/ecdsa/ecdsa.go
index 22ce08e79..74f52145a 100644
--- a/ecc/bls12-378/ecdsa/ecdsa.go
+++ b/ecc/bls12-378/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bls12-381/ecdsa/ecdsa.go b/ecc/bls12-381/ecdsa/ecdsa.go
index 4aea1575c..9944b8954 100644
--- a/ecc/bls12-381/ecdsa/ecdsa.go
+++ b/ecc/bls12-381/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bls24-315/ecdsa/ecdsa.go b/ecc/bls24-315/ecdsa/ecdsa.go
index d9b7362d0..747f3fca4 100644
--- a/ecc/bls24-315/ecdsa/ecdsa.go
+++ b/ecc/bls24-315/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bls24-317/ecdsa/ecdsa.go b/ecc/bls24-317/ecdsa/ecdsa.go
index add547cb2..4fb8355e8 100644
--- a/ecc/bls24-317/ecdsa/ecdsa.go
+++ b/ecc/bls24-317/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bn254/ecdsa/ecdsa.go b/ecc/bn254/ecdsa/ecdsa.go
index c860e7b94..dcde60137 100644
--- a/ecc/bn254/ecdsa/ecdsa.go
+++ b/ecc/bn254/ecdsa/ecdsa.go
@@ -35,6 +35,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -101,7 +102,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bw6-633/ecdsa/ecdsa.go b/ecc/bw6-633/ecdsa/ecdsa.go
index e744f91d4..649a8efe0 100644
--- a/ecc/bw6-633/ecdsa/ecdsa.go
+++ b/ecc/bw6-633/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bw6-756/ecdsa/ecdsa.go b/ecc/bw6-756/ecdsa/ecdsa.go
index e3914a732..bf32e9cac 100644
--- a/ecc/bw6-756/ecdsa/ecdsa.go
+++ b/ecc/bw6-756/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/bw6-761/ecdsa/ecdsa.go b/ecc/bw6-761/ecdsa/ecdsa.go
index 4665a1f17..0c77b0b0b 100644
--- a/ecc/bw6-761/ecdsa/ecdsa.go
+++ b/ecc/bw6-761/ecdsa/ecdsa.go
@@ -34,6 +34,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -100,7 +101,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/secp256k1/ecdsa/ecdsa.go b/ecc/secp256k1/ecdsa/ecdsa.go
index f1489bd65..6c633fc99 100644
--- a/ecc/secp256k1/ecdsa/ecdsa.go
+++ b/ecc/secp256k1/ecdsa/ecdsa.go
@@ -35,6 +35,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = 2 * sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -101,7 +102,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/ecc/stark-curve/ecdsa/ecdsa.go b/ecc/stark-curve/ecdsa/ecdsa.go
index 0523fa1e2..5d94cd791 100644
--- a/ecc/stark-curve/ecdsa/ecdsa.go
+++ b/ecc/stark-curve/ecdsa/ecdsa.go
@@ -35,6 +35,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 	sizePublicKey  = sizeFp
 	sizePrivateKey = sizeFr + sizePublicKey
@@ -101,7 +102,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
 	}
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}
diff --git a/internal/generator/ecdsa/template/ecdsa.go.tmpl b/internal/generator/ecdsa/template/ecdsa.go.tmpl
index ff966d73a..1dda1ed34 100644
--- a/internal/generator/ecdsa/template/ecdsa.go.tmpl
+++ b/internal/generator/ecdsa/template/ecdsa.go.tmpl
@@ -19,6 +19,7 @@ import (
 
 const (
 	sizeFr         = fr.Bytes
+	sizeFrBits     = fr.Bits
 	sizeFp         = fp.Bytes
 {{- if eq .Name "secp256k1"}}
 	sizePublicKey  = 2 * sizeFp
@@ -94,7 +95,7 @@ func HashToInt(hash []byte) *big.Int {
 		hash = hash[:sizeFr]
     }
 	ret := new(big.Int).SetBytes(hash)
-	excess := len(hash)*8 - sizeFr
+	excess := ret.BitLen() - sizeFrBits
 	if excess > 0 {
 		ret.Rsh(ret, uint(excess))
 	}