From 4ab48d2323630b702b6a07adb0966d1ef836eb4d Mon Sep 17 00:00:00 2001
From: Mostafa <mostafa.sedaghat@gmail.com>
Date: Wed, 16 Jul 2025 18:45:37 +0800
Subject: [PATCH 1/2] feat: split secret for BLS

---
 README.md                         |  2 +-
 examples/example_bls_threshold.py | 31 +++++++++++++++++++++++++++++++
 pactus/crypto/bls/private_key.py  | 24 ++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 examples/example_bls_threshold.py

diff --git a/README.md b/README.md
index 075687a..dfc16a2 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ Explore the `examples` folder for more detailed usage scenarios.
 For local development, you can install the package in editable mode, which allows you to make changes and test them immediately:
 
 ```bash
-python3 -m pip install .
+python3 -m pip install -e .
 ```
 
 After making changes, it's important to ensure all tests pass by running:
diff --git a/examples/example_bls_threshold.py b/examples/example_bls_threshold.py
new file mode 100644
index 0000000..bd7bfed
--- /dev/null
+++ b/examples/example_bls_threshold.py
@@ -0,0 +1,31 @@
+from pactus.crypto.bls.private_key import PrivateKey
+from pactus.crypto.bls.signature import Signature
+from itertools import combinations
+
+
+
+# Example of BLS threshold signature aggregation using Shamir's Secret Sharing
+# This example demonstrates how to create a threshold signature scheme
+# where a subset of signers can create a valid signature.
+
+
+def main() -> None:
+    msg = "some message".encode()
+    N = 3  # Number of signers
+    T = 2  # Threshold for aggregation
+
+    msk = PrivateKey.random() # Master Secret Key
+    mpk = msk.public_key()
+
+    print(f"Master Secret Key: {msk.raw_bytes().hex()}")
+    print(f"Master Public Key: {mpk.string()}")
+
+    shares = msk.split(N, T)
+
+    for i, sk in enumerate(shares):
+        print(f"Private Key Share {i + 1}: {sk.raw_bytes().hex()}")
+
+
+
+if __name__ == "__main__":
+    main()
diff --git a/pactus/crypto/bls/private_key.py b/pactus/crypto/bls/private_key.py
index 48830a6..fc4ac25 100644
--- a/pactus/crypto/bls/private_key.py
+++ b/pactus/crypto/bls/private_key.py
@@ -79,3 +79,27 @@ def public_key(self) -> PublicKey:
     def sign(self, msg: bytes) -> Signature:
         point_g1 = sign(self.scalar, msg, ciphersuite=DST)
         return Signature(point_g1)
+
+    def split(self, n: int, t: int) -> list[PrivateKey]:
+        if n < t:
+            raise ValueError("n must be greater than t")
+
+        if n < 1:
+            raise ValueError("n must be greater than 0")
+
+        # Create the coefficients for the polynomial: c[0] = secret, c[1..t-1] = random private keys
+        coeffs = [self.scalar]
+        for _ in range(1, t):
+            rand_priv = PrivateKey.random()
+            coeffs.append(rand_priv.scalar)
+
+        # Generate n shares by evaluating the polynomial at x = 1..n
+        shares = []
+        for i in range(1, n + 1):
+            share_scalar = utils.evaluate_polynomial(coeffs, i, curve_order)
+            if share_scalar is None:
+                raise ValueError(f"Failed to evaluate polynomial at x={i}")
+            shares.append(PrivateKey(share_scalar))
+
+        return shares
+

From 59934c1ee886771067778f94ad8d22b641987d96 Mon Sep 17 00:00:00 2001
From: Mostafa <mostafa.sedaghat@gmail.com>
Date: Wed, 16 Jul 2025 18:54:59 +0800
Subject: [PATCH 2/2] chore: fix linting issues

---
 examples/example_bls_threshold.py |  8 ++------
 pactus/crypto/bls/private_key.py  | 11 +++++++----
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/examples/example_bls_threshold.py b/examples/example_bls_threshold.py
index bd7bfed..49ef299 100644
--- a/examples/example_bls_threshold.py
+++ b/examples/example_bls_threshold.py
@@ -1,7 +1,4 @@
 from pactus.crypto.bls.private_key import PrivateKey
-from pactus.crypto.bls.signature import Signature
-from itertools import combinations
-
 
 
 # Example of BLS threshold signature aggregation using Shamir's Secret Sharing
@@ -10,11 +7,11 @@
 
 
 def main() -> None:
-    msg = "some message".encode()
+    # msg = "some message".encode()
     N = 3  # Number of signers
     T = 2  # Threshold for aggregation
 
-    msk = PrivateKey.random() # Master Secret Key
+    msk = PrivateKey.random()  # Master Secret Key
     mpk = msk.public_key()
 
     print(f"Master Secret Key: {msk.raw_bytes().hex()}")
@@ -26,6 +23,5 @@ def main() -> None:
         print(f"Private Key Share {i + 1}: {sk.raw_bytes().hex()}")
 
 
-
 if __name__ == "__main__":
     main()
diff --git a/pactus/crypto/bls/private_key.py b/pactus/crypto/bls/private_key.py
index fc4ac25..3027e0c 100644
--- a/pactus/crypto/bls/private_key.py
+++ b/pactus/crypto/bls/private_key.py
@@ -82,10 +82,12 @@ def sign(self, msg: bytes) -> Signature:
 
     def split(self, n: int, t: int) -> list[PrivateKey]:
         if n < t:
-            raise ValueError("n must be greater than t")
+            msg = f"n must be greater than t: n={n}, t={t}"
+            raise ValueError(msg)
 
         if n < 1:
-            raise ValueError("n must be greater than 0")
+            msg = f"n must be greater than 1: n={n}"
+            raise ValueError(msg)
 
         # Create the coefficients for the polynomial: c[0] = secret, c[1..t-1] = random private keys
         coeffs = [self.scalar]
@@ -98,8 +100,9 @@ def split(self, n: int, t: int) -> list[PrivateKey]:
         for i in range(1, n + 1):
             share_scalar = utils.evaluate_polynomial(coeffs, i, curve_order)
             if share_scalar is None:
-                raise ValueError(f"Failed to evaluate polynomial at x={i}")
+                msg = f"Failed to evaluate polynomial at x={i}"
+                raise ValueError(msg)
+
             shares.append(PrivateKey(share_scalar))
 
         return shares
-