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+```
+#!htmlcomment
+
+This page is maintained automatically by a script.  Don't modify this page by hand,
+your changes will just be overwritten the next time the script runs.  Talk to your
+Friendly Neighborhood Repository Maintainer if you need to change something here.
+
+```
+
+```
+#!html
+<h1>sha256</h1>
+
+<p>Hardware implementation of the SHA-256 cryptographic hash function. The
+implementation is written in Verilog 2001 compliant code. The
+implementation includes a core and a wrapper that provides a 32-bit
+interface for simple integration. There is also an alternative wrapper
+that implements a Wishbone compliant interface.</p>
+
+<p>This is a low area implementation that iterates over the rounds but
+there is no sharing of operations such as adders.</p>
+
+<p>The hardware implementation is complemented by a functional model
+written in Python.</p>
+
+<h2>Implementation details</h2>
+
+<p>The sha256 is divided into the following sections.</p>
+
+<ul>
+<li>src/rtl - RTL source files</li>
+<li>src/tb  - Testbenches for the RTL files</li>
+<li>src/model/python - Functional model written in python</li>
+<li>doc - documentation (currently not done.)</li>
+<li>toolruns - Where tools are supposed to be run. Includes a Makefile for
+building and simulating the design using <a href="http://iverilog.icarus.com/">Icarus Verilog</a></li>
+</ul>
+
+<p>The actual core consists of the following files:</p>
+
+<ul>
+<li>sha256_core.v - The core itself with wide interfaces.</li>
+<li>sha256_w_mem.v - W message block memort and expansion logic.</li>
+<li>sha256_k_constants.v - K constants ROM memory.</li>
+</ul>
+
+<p>The top level entity is called sha256_core. This entity has wide
+interfaces (512 bit block input, 256 bit digest). In order to make it
+usable you probably want to wrap the core with a bus interface.</p>
+
+<p>Unless you want to provide your own interface you therefore also need to
+select one top level wrapper. There are two wrappers provided:</p>
+
+<ul>
+<li>sha256.v - A wrapper with a 32-bit memory like interface.</li>
+<li>wb_sha256.v - A wrapper that implements a <a href="http://opencores.org/opencores,wishbone">Wishbone</a> interface.</li>
+</ul>
+
+<p><strong><em>Do not include both wrappers in the same project.</em></strong></p>
+
+<p>The core (sha256_core) will sample all data inputs when given the init
+or next signal. the wrappers provided contains additional data
+registers. This allows you to load a new block while the core is
+processing the previous block.</p>
+
+<p>The W-memory scheduler is based on 16 32-bit registers. Thee registers
+are loaded with the current block. After 16 rounds the contents of the
+registers slide through the registers r5..r0 while the new W word is
+inserted at r15 as well as being returned to the core.</p>
+
+<h2>FPGA-results</h2>
+
+<h3>Altera Cyclone FPGAs</h3>
+
+<p>Implementation results using Altera Quartus-II 13.1.</p>
+
+<p><strong><em>Cyclone IV E</em></strong></p>
+
+<ul>
+<li>EP4CE6F17C6</li>
+<li>3882 LEs</li>
+<li>1813 registers</li>
+<li>74 MHz</li>
+<li>66 cycles latency</li>
+</ul>
+
+<p><strong><em>Cyclone IV GX</em></strong></p>
+
+<ul>
+<li>EP4CGX22CF19C6</li>
+<li>3773 LEs</li>
+<li>1813 registers</li>
+<li>76 MHz</li>
+<li>66 cycles latency</li>
+</ul>
+
+<p><strong><em>Cyclone V</em></strong></p>
+
+<ul>
+<li>5CGXFC7C7F23C8</li>
+<li>1469 ALMs</li>
+<li>1813 registers</li>
+<li>79 MHz</li>
+<li>66 cycles latency</li>
+</ul>
+
+<h3>Xilinx Artix-7 FPGAs</h3>
+
+<p>Implementation results using Xilinx ISE 14.7
+This implementation includes pipeline regsisters.</p>
+
+<ul>
+<li>xc7a200t-1fbg484</li>
+<li>2229 Slice LUTs</li>
+<li>775 Slices</li>
+<li>1935 registers</li>
+<li>101 MHz</li>
+<li>130 cycles latency</li>
+</ul>
+
+<h2>TODO</h2>
+
+<ul>
+<li>Extensive verification in physical device.</li>
+<li>Complete documentation.</li>
+</ul>
+
+<h2>Status</h2>
+
+<p><strong><em>(2016-05-31)</em></strong></p>
+
+<p>The core now supports both sha224 and sha256 modes. The default mode is
+sha256.</p>
+
+<p>NOTE: The mode bit is located in the ADDR_CTRL API register and this
+means that when writing to this register to start processing a block,
+care must be taken to set the mode bit to the intended mode. This means
+that old code that for example simply wrote 0x01 to initiate SHA256
+processing will now initiate SHA224 processing. Writing 0x05 will
+now initiate SHA256 processing.</p>
+
+<p>The API version has been bumped a major number to reflect this change.</p>
+
+<p>Regarding SHA224, it is up to the user to only read seven, not eight
+words from the digest registers. The core will update the LSW too.</p>
+
+<p><strong><em>(2013-02-23)</em></strong></p>
+
+<p>Cleanup, more results etc. Move all wmem update logic to a separate
+process for a cleaner code.</p>
+
+<p><strong>(2014-02-22)</strong></p>
+
+<p>Redesigned the W-memory into a sliding window solution. This not only
+removed 48 32-registers but also several muxes and address decoders.</p>
+
+<p>The old implementation resources and performance:</p>
+
+<ul>
+<li>9587 LEs</li>
+<li>3349 registers</li>
+<li>73 MHz</li>
+<li>66 cycles latency</li>
+</ul>
+
+<p>The new implementation resources and performance:</p>
+
+<ul>
+<li>3765 LEs</li>
+<li>1813 registers</li>
+<li>76 MHz</li>
+<li>66 cycles latency</li>
+</ul>
+
+<p><strong>(2014-02-19)</strong>
+- The core has been added to the Cryptech repo. The core comes from
+  https://github.com/secworks/sha256</p>
+```
+
+[[RepositoryIndex(format=table,glob=core/hash/sha256)]]
+
+| Clone `https://git.cryptech.is/core/hash/sha256.git` |
+|---|