bigchaindb/docs/build/html/Cryptography.html
2016-02-09 19:16:18 +01:00

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<p>Cryptographic algorithms and python implementations that we use.</p>
<p>The implementations that we have chosen for now are just for fast prototyping. Some of them are pure python
implementations which may be slow. As future work we should look at other alternatives</p>
<div class="section" id="hashes">
<span id="hashes"></span><h1>Hashes<a class="headerlink" href="#hashes" title="Permalink to this headline"></a></h1>
<p>For hashing we are using the sha3-256 algorithm and <a class="reference external" href="https://bitbucket.org/tiran/pykeccak">pysha3</a> as the python
implementation. We store the hex encoded hash in the bigchain.</p>
<div class="section" id="example">
<span id="example"></span><h2>Example<a class="headerlink" href="#example" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">hashlib</span>
<span class="c1"># monkey patch hashlib with sha3 functions</span>
<span class="kn">import</span> <span class="nn">sha3</span>
<span class="n">data</span> <span class="o">=</span> <span class="s2">&quot;message&quot;</span>
<span class="n">tx_hash</span> <span class="o">=</span> <span class="n">hashlib</span><span class="o">.</span><span class="n">sha3_256</span><span class="p">(</span><span class="n">data</span><span class="p">)</span><span class="o">.</span><span class="n">hexdigest</span><span class="p">()</span>
</pre></div>
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<div class="section" id="keys">
<span id="keys"></span><h1>Keys<a class="headerlink" href="#keys" title="Permalink to this headline"></a></h1>
<p>For signing and veryfing signatures we are using the ECDSA with 192bit key lengths and
<a class="reference external" href="https://github.com/warner/python-ecdsa">python-ecdsa</a> as the python implementation.</p>
<p>The public-key or verification key are converted to string and hex encoded before storing them to the blockchain</p>
<div class="section" id="example">
<span id="id1"></span><h2>Example<a class="headerlink" href="#example" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">binascii</span>
<span class="kn">from</span> <span class="nn">ecdsa</span> <span class="kn">import</span> <span class="n">SigningKey</span>
<span class="c1"># generate signing key in hex encoded form</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">SigningKey</span><span class="o">.</span><span class="n">generate</span><span class="p">()</span>
<span class="n">sk_hex</span> <span class="o">=</span> <span class="n">binascii</span><span class="o">.</span><span class="n">hexlify</span><span class="p">(</span><span class="n">sk</span><span class="o">.</span><span class="n">to_string</span><span class="p">())</span>
<span class="c1"># get signing key from hex</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">SigningKey</span><span class="o">.</span><span class="n">from_string</span><span class="p">(</span><span class="n">binascii</span><span class="o">.</span><span class="n">unhexlify</span><span class="p">(</span><span class="n">sk_hex</span><span class="p">))</span>
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<h3><a href="index.html">Table Of Contents</a></h3>
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<li><a class="reference internal" href="#">Hashes</a><ul>
<li><a class="reference internal" href="#example">Example</a></li>
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<li><a class="reference internal" href="#keys">Keys</a><ul>
<li><a class="reference internal" href="#example">Example</a></li>
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