From 6a82f81a31c579a7ae8715ad49e70e5f7c88318e Mon Sep 17 00:00:00 2001
From: Ringoshiro <137809157+Ringoshiroku@users.noreply.github.com>
Date: Sun, 19 Oct 2025 02:59:14 +0700
Subject: [PATCH 1/2] added crypto/bcc

---
 Cryptography/bcc/README.md       |  1 +
 Cryptography/bcc/challenge.yml   | 29 +++++++++++++++++++++
 Cryptography/bcc/dist/chall.py   | 43 ++++++++++++++++++++++++++++++++
 Cryptography/bcc/dist/output.txt |  5 ++++
 Cryptography/bcc/src/flag.txt    |  1 +
 5 files changed, 79 insertions(+)
 create mode 100644 Cryptography/bcc/README.md
 create mode 100644 Cryptography/bcc/challenge.yml
 create mode 100644 Cryptography/bcc/dist/chall.py
 create mode 100644 Cryptography/bcc/dist/output.txt
 create mode 100644 Cryptography/bcc/src/flag.txt

diff --git a/Cryptography/bcc/README.md b/Cryptography/bcc/README.md
new file mode 100644
index 0000000..0f71901
--- /dev/null
+++ b/Cryptography/bcc/README.md
@@ -0,0 +1 @@
+# BCC
\ No newline at end of file
diff --git a/Cryptography/bcc/challenge.yml b/Cryptography/bcc/challenge.yml
new file mode 100644
index 0000000..f036a05
--- /dev/null
+++ b/Cryptography/bcc/challenge.yml
@@ -0,0 +1,29 @@
+name: "BCC"
+category: Cryptography
+description: |-
+  Beelliptic Curve Cryptography, or BCC, is a cryptographic scheme based on the mathematical properties of bees and elliptic curves. Buzzing with security, BCC offers a unique approach to encryption and digital signatures, making it a sweet choice for protecting sensitive information in the digital age. Your task is to exploit the weaknesses in the BCC implementation to retrieve the flag.
+
+  Author: ringoshiro
+
+##### DON'T CHANGE
+value: 500
+type: dynamic
+extra:
+    initial: 500
+    decay: 30
+    minimum: 100
+##### DON'T CHANGE
+
+flags:
+  - BEECTF{4uth0r_n33d5_r3st_n0w...}
+
+tags:
+  - medium
+
+files:
+  - dist/chall.py
+  - dist/output.txt
+
+state: hidden
+
+version: "0.1"
diff --git a/Cryptography/bcc/dist/chall.py b/Cryptography/bcc/dist/chall.py
new file mode 100644
index 0000000..0958575
--- /dev/null
+++ b/Cryptography/bcc/dist/chall.py
@@ -0,0 +1,43 @@
+from secret import p, a, b, G, BETA
+
+def add(P, Q, a, p):
+    if P is None:
+        return Q
+    if Q is None:
+        return P
+    x1, y1 = P
+    x2, y2 = Q
+    if x1 == x2 and (y1 != y2 or y1 == 0):
+        return None
+    if x1 == x2:
+        m = (3 * x1 * x1 + a) * pow(2 * y1, -1, p) % p
+    else:
+        m = (y2 - y1) * pow(x2 - x1, -1, p) % p
+    x3 = (m * m - x1 - x2) % p
+    y3 = (m * (x1 - x3) - y1) % p
+    return (x3, y3)
+
+def mul(k, P, a, p):
+    R0 = None
+    R1 = P
+    for bit in bin(k)[2:]:
+        if bit == '0':
+            R1 = add(R0, R1, a, p)
+            R0 = add(R0, R0, a, p)
+        else:
+            R0 = add(R0, R1, a, p)
+            R1 = add(R1, R1, a, p)
+    return R0
+
+flag = int.from_bytes(b"BEECTF{xxxxxxxxxxxxxxxxxxxxxxxx}")
+kprime = (flag + BETA) % (p - 1)
+
+Gx = G[0]
+Qx = mul(kprime, G, a, p)[0]
+Rx = mul(BETA, G, a, p)[0]
+
+print(f'{p = }')
+print(f'{a = }')
+print(f'{Gx = }')
+print(f'{Qx = }')
+print(f'{Rx = }')
\ No newline at end of file
diff --git a/Cryptography/bcc/dist/output.txt b/Cryptography/bcc/dist/output.txt
new file mode 100644
index 0000000..03009c8
--- /dev/null
+++ b/Cryptography/bcc/dist/output.txt
@@ -0,0 +1,5 @@
+p = 3059506932006842768669313045979965122802573567548630439761719809964279577239571933
+a = 2448848303492708630919982332575904911263442803797664768836842024937962142592572096
+Gx = 1175626665511163128867519385055567089318632886502007689116591740322574196248254667
+Qx = 1692192797051786849921937448962108889305900850182074908387601492835973879030967392
+Rx = 432244659212727282574552361819256527291075425049776311256018620682846747709939971
\ No newline at end of file
diff --git a/Cryptography/bcc/src/flag.txt b/Cryptography/bcc/src/flag.txt
new file mode 100644
index 0000000..1b64480
--- /dev/null
+++ b/Cryptography/bcc/src/flag.txt
@@ -0,0 +1 @@
+BEECTF{4uth0r_n33d5_r3st_n0w...}
\ No newline at end of file

From d067b927253f7aaf716a31d941bb9cfbd6241d8a Mon Sep 17 00:00:00 2001
From: Ringoshiro <137809157+Ringoshiroku@users.noreply.github.com>
Date: Sun, 19 Oct 2025 03:12:08 +0700
Subject: [PATCH 2/2] fix: attempting change in yml file

---
 Cryptography/bcc/README.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Cryptography/bcc/README.md b/Cryptography/bcc/README.md
index 0f71901..ca59c68 100644
--- a/Cryptography/bcc/README.md
+++ b/Cryptography/bcc/README.md
@@ -1 +1,3 @@
-# BCC
\ No newline at end of file
+# BCC
+
+to-do
\ No newline at end of file