From b2b6708e8f00fd1a70b62b936e88528453ab9e14 Mon Sep 17 00:00:00 2001
From: Mark Qvist <mark@unsigned.io>
Date: Tue, 7 Jun 2022 17:32:22 +0200
Subject: [PATCH] Added python-only implementation of PKCS7 padding

---
 RNS/Cryptography/PKCS7.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 RNS/Cryptography/PKCS7.py

diff --git a/RNS/Cryptography/PKCS7.py b/RNS/Cryptography/PKCS7.py
new file mode 100644
index 0000000..acffa63
--- /dev/null
+++ b/RNS/Cryptography/PKCS7.py
@@ -0,0 +1,18 @@
+class PKCS7:
+    BLOCKSIZE = 16
+
+    @staticmethod
+    def pad(data, bs=BLOCKSIZE):
+        l = len(data)
+        n = bs-l%bs
+        v = bytes([n])
+        return data+v*n
+
+    @staticmethod
+    def unpad(data, bs=BLOCKSIZE):
+        l = len(data)
+        n = data[-1]
+        if n > bs:
+            raise ValueError("Cannot unpad, invalid padding length of "+str(n)+" bytes")
+        else:
+            return data[:l-n]
\ No newline at end of file