Welcome to ``cryptography`` =========================== ``cryptography`` is a Python library which exposes cryptographic recipes and primitives. Our goal is for it to be your "cryptographic standard library". If you are interested in learning more about the field of cryptography, we recommend `Crypto 101, by Laurens Van Houtven`_. Installation ------------ You can install ``cryptography`` with ``pip``: .. code-block:: console $ pip install cryptography See :doc:`Installation ` for more information. Why a new crypto library for Python? ------------------------------------ If you've done cryptographic work in Python before, you've probably seen some other libraries in Python, such as *M2Crypto*, *PyCrypto*, or *PyOpenSSL*. In building ``cryptography`` we wanted to address a few issues we observed in the existing libraries: * Lack of PyPy and Python 3 support. * Lack of maintenance. * Use of poor implementations of algorithms (i.e. ones with known side-channel attacks). * Lack of high level, "Cryptography for humans", APIs. * Absence of algorithms such as :class:`AES-GCM ` and :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`. * Poor introspectability, and thus poor testability. * Extremely error prone APIs, and bad defaults. .. _cryptography-layout: Layout ------ ``cryptography`` is broadly divided into two levels. One with safe cryptographic recipes, "cryptography for humans" if you will. These are safe and easy to use and don't require developers to make many decisions. The other level is low-level cryptographic primitives. These are often dangerous and can be used incorrectly. They require making decisions and having an in-depth knowledge of the cryptographic concepts at work. Because of the potential danger in working at this level, this is referred to as the "hazardous materials" or "hazmat" layer. These live in the ``cryptography.hazmat`` package, and their documentation will always contain an admonition at the top. We recommend using the recipes layer whenever possible, and falling back to the hazmat layer only when necessary. The recipes layer ~~~~~~~~~~~~~~~~~ .. toctree:: :maxdepth: 2 fernet random-numbers exceptions faq glossary x509 The hazardous materials layer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. toctree:: :maxdepth: 2 hazmat/primitives/index hazmat/backends/index hazmat/bindings/index The ``cryptography`` open source project ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. toctree:: :maxdepth: 2 installation development/index security limitations api-stability doing-a-release changelog community .. note:: ``cryptography`` has not been subjected to an external audit of its code or documentation. If you're interested in discussing an audit please :doc:`get in touch `. .. _`Crypto 101, by Laurens Van Houtven`: https://www.crypto101.io/ e>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
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<title>YosysJS Example Application #02</title>
<script type="text/javascript" src="yosysjs.js"></script>
<script src="http://wavedrom.com/skins/default.js" type="text/javascript"></script>
<script src="http://wavedrom.com/WaveDrom.js" type="text/javascript"></script>
<style type="text/css">
.noedit { color: #666; }
</style>
<script id="golden_verilog" type="text/plain">
module ref(input clk, reset, input [7:0] A, output reg [7:0] Y);
	always @(posedge clk) begin
		if (reset)
			Y <= 0;
		else
			Y <= ((Y << 5) + Y) ^ A;
	end
endmodule
</script>
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	</div>
	<h1>YosysJS Example Application #03</h1>
	<b>Your mission:</b> Create a behavioral Verilog model for the following circuit:
	<p/>
	<div id="main" style="visibility: hidden">
		<svg id="schem" width="800"></svg>
		<p/>
		<pre id="code" style="width: 800px; border:2px solid #000; padding: 0.5em;"><span class="noedit">module top(input clk, reset, input [7:0] A, output reg [7:0] Y);
  always @(posedge clock) begin</span><span class="edit" contenteditable="true">
    Y &lt;= A | {4{reset}};
  </span><span class="noedit">end
endmodule</span></pre><p/>
		<input type="button" value="Check Model" onclick="check_model()"> <span id="checkmessage"></span>
		<p/>
		<p id="wave">&nbsp;</p>
	</div>
	<script type="text/javascript">
		function on_ys_ready() {
			ys.write_file('golden.v', document.getElementById('golden_verilog').textContent);
			ys.run('echo on; read_verilog golden.v; proc;;');
			ys.run('show -notitle -width -stretch');
			YosysJS.dot_into_svg(ys.read_file('show.dot'), 'schem');
			document.getElementById('popup').style.visibility = 'hidden';
			document.getElementById('popupmsg').textContent = 'Please wait..';
			document.getElementById('main').style.visibility = 'visible';
		}
		function check_model() {
			function work() {
				ys.remove_file('wave.json');
				ys.write_file('code.v', document.getElementById('code').textContent);
				ys.errmsg = '';
				ys.run('design -reset; read_verilog code.v; hierarchy -top top; proc; opt; flatten; hierarchy; ' +
					'read_verilog golden.v; proc; miter -equiv -ignore_gold_x -make_outputs -flatten ref top miter; ' +
					'hierarchy -top miter; clean -purge; sat -set-init-undef -seq 8 -dump_json wave.json -show-ports ' +
					'-max_undef -prove trigger 0 miter');
				w = document.getElementById('wave')
				if (ys.errmsg) {
					w.innerHTML = '<b><pre>ERROR: ' + ys.errmsg.replace('&', '&amp;').replace('<', '&lt;').replace('>', '&gt;') + '</pre></b>';
				} else {
					wdata = ys.read_file('wave.json');
					if (wdata) {
						wdata = JSON.parse(wdata);
						function wsignal(signame, newname) {
							for (i = 0; i < wdata["signal"].length; i++)
								if (wdata["signal"][i].name == signame) {
									if (newname)
										wdata["signal"][i].name = newname;
									return wdata["signal"][i];
								}
							return {};
						}
						wdata2 = {
							"signal" : [
								{ name: 'clk', wave: 'P........' },
								wsignal("trigger"),
								{},
								[ "Inputs", wsignal("in_reset", "reset"), wsignal("in_A", "A") ],
								{},
								[ "Y Output", wsignal("gold_Y", "Ref"), wsignal("gate_Y", "UUT") ],
							],
							"config" : wdata["config"]
						};
						wdata2 = JSON.stringify(wdata2)
						w.innerHTML = '<b>The model did not pass verification:</b><p/>' +
								'<script type="WaveDrom">' + wdata2 + '<\/script>';
						WaveDrom.ProcessAll();
					} else {
						w.innerHTML = '<b>Congratulations! The model did pass verification.</b><p/>';
					}
				}
				document.getElementById('popup').style.visibility = 'hidden';
			}
			document.getElementById('popup').style.visibility = 'visible';
			window.setTimeout(work, 100);
		}

		YosysJS.load_viz();
		var ys = YosysJS.create('', on_ys_ready);
		ys.logprint = true;
	</script>
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