1 files changed, 130 insertions, 0 deletions
diff --git a/notebooks/cryptography_experiments.ipynb b/notebooks/cryptography_experiments.ipynb
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+++ b/notebooks/cryptography_experiments.ipynb
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+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 31,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import os\n",
+    "\n",
+    "import hashlib\n",
+    "import nacl.signing\n",
+    "from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes\n",
+    "from cryptography.hazmat.backends import default_backend"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sign_key = nacl.signing.SigningKey.generate()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 44,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "make_action_string = lambda group, index: f'reset idx={index:08x} g={group}'.encode()\n",
+    "def generate_presig(group, index):\n",
+    "    action_string = make_action_string(group, index)\n",
+    "    sig = sign_key.sign(action_string)[:64] # cut off original message\n",
+    "    \n",
+    "    key = os.urandom(16)\n",
+    "    \n",
+    "    cipher = Cipher(algorithms.AES(key), modes.CTR(b'\\0' * 16), backend=default_backend())\n",
+    "    enc = cipher.encryptor()\n",
+    "    ciphtertext = enc.update(sig)\n",
+    "    assert len(enc.finalize()) == 0\n",
+    "    \n",
+    "    return key, ciphtertext\n",
+    "\n",
+    "presigs = { group: [ generate_presig(group, index) for index in range(64) ] for group in ['all', 'v=foo', 's=bar', 'l=somewhere'] }"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 46,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(b'\\x9f\\n\\x8e\\xc9\\x1d\\xaf*\\xac\\x9e\\x1as\\xe8\\xf8\\xe6\\xe9z',\n",
+       " b'{\\xd8\\xb4\\xaf\\xb4PK1%*`\\\\\\x8e\\x93;\\x82\\xeaF\\x99\\xe0\\xbfB\\xf1\\x9d\\xae\\x02|\\xae\\\\?\\x97\\xb3\\xa5j.Y\\x83\\xddg\\x7f\\x06\\xd2\\xa47^\\xf3\\xdd\\x08n3\\x90\\x84~\\x96,tO#\\x8e$\\xdc\\xa2\\x1a\\r')"
+      ]
+     },
+     "execution_count": 46,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "presigs['all'][0]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 69,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def validate_presig(group, index, key, presig, verify_key=sign_key.verify_key):\n",
+    "    \"\"\" Will raise an error for invalid signature or group/index \"\"\"\n",
+    "    action_string = make_action_string(group, index)\n",
+    "    \n",
+    "    cipher = Cipher(algorithms.AES(key), modes.CTR(b'\\0' * 16), backend=default_backend())\n",
+    "    dec = cipher.decryptor()\n",
+    "    plaintext = dec.update(presig)\n",
+    "    assert len(dec.finalize()) == 0\n",
+    "    \n",
+    "    return verify_key.verify(plaintext + action_string) == action_string"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 70,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 70,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "validate_presig('all', 0, *presigs['all'][0])"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "labenv",
+   "language": "python",
+   "name": "labenv"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.8.2"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}