pyUmbral/docs/notebooks/pyUmbral Simple API.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# pyUmbral python API"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Setting the default curve\n",
    "\n",
    "The first time you use umbral, you may want to specify an elliptic curve to use.  If you do not specify a curve, secp256k1 will be used for all operations, with a slight performace hit for the lookup.\n",
    "\n",
    "To set the default curve use `umbral.config.set_default_curve()`\n",
    "\n",
    "Note: you can only set the dafault once, or `UmbralConfigurationError` will be raised."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from umbral.config import set_default_curve\n",
    "from cryptography.hazmat.primitives.asymmetric import ec\n",
    "\n",
    "set_default_curve(ec.SECP256K1)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Generate Umbral Keys"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "from umbral import keys\n",
    "\n",
    "\n",
    "# Alice's Keys\n",
    "alice_private_key = keys.UmbralPrivateKey.gen_key()\n",
    "alice_public_key = alice_private_key.get_pubkey()\n",
    "\n",
    "# Bob's Keys\n",
    "bob_private_key = keys.UmbralPrivateKey.gen_key()\n",
    "bob_public_key = bob_private_key.get_pubkey()\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Alice encrypts data; Generates a capsule"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "from umbral import umbral\n",
    "\n",
    "\n",
    "plaintext = b'attack at dawn'\n",
    "ciphertext, capsule = umbral.encrypt(alice_public_key, plaintext)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Alice decrypts data for self"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "b'attack at dawn'\n"
     ]
    }
   ],
   "source": [
    "cleartext = umbral.decrypt(capsule, alice_private_key, ciphertext)\n",
    "print(cleartext)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Proxy Re-encryption\n",
    "\n",
    "![proxy_reencryption](https://cdn-images-1.medium.com/max/1200/0*yTKUeeuKPu-aIZdw.)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Split Rekeys"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "N, M = 1, 1\n",
    "kfrags, vkeys = umbral.split_rekey(alice_private_key, bob_public_key, M, N)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\n",
    "## Ursula Re-encrypts; Bob attaches fragments to capsule\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "for kfrag in kfrags:\n",
    "    cfrag = umbral.reencrypt(kfrag, capsule)\n",
    "    capsule.attach_cfrag(cfrag)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Bob activates and opens the capsule; Decrypts data from Alice."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "b'attack at dawn'\n"
     ]
    }
   ],
   "source": [
    "reencrypted_cleartext = umbral.decrypt(capsule, bob_private_key, ciphertext, alice_public_key)\n",
    "print(reencrypted_cleartext)\n"
   ]
  }
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