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<p>We need to clearly define how to serialize a json object to calculate the hash.</p>
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<p>The serialization should produce the same byte output independently of the architecture running the software. If
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there are diferences in the serialization hash validations will fail altough the transaction is correct</p>
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<div class="section" id="example">
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<span id="example"></span><h1>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h1>
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<div class="highlight-python"><div class="highlight"><pre><span class="n">a</span> <span class="o">=</span> <span class="n">r</span><span class="o">.</span><span class="n">expr</span><span class="p">({</span><span class="s1">'a'</span><span class="p">:</span> <span class="mi">1</span><span class="p">})</span><span class="o">.</span><span class="n">to_json</span><span class="p">()</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">b</span><span class="o">.</span><span class="n">connection</span><span class="p">)</span>
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<span class="s1">u'{"a":1}'</span>
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<span class="n">b</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">({</span><span class="s1">'a'</span><span class="p">:</span> <span class="mi">1</span><span class="p">})</span>
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<span class="s1">'{"a": 1}'</span>
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<span class="n">a</span> <span class="o">==</span> <span class="n">b</span>
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<span class="bp">False</span>
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</pre></div>
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</div>
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<p>We should provide the serialization and deserialization so that the following is always true.</p>
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</div>
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<div class="section" id="example">
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<span id="id1"></span><h1>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h1>
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<div class="highlight-python"><div class="highlight"><pre><span class="n">deserialize</span><span class="p">(</span><span class="n">serialize</span><span class="p">(</span><span class="n">data</span><span class="p">))</span> <span class="o">==</span> <span class="n">data</span>
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<span class="bp">True</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="standard-serialization-for-the-bigchain">
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<span id="standard-serialization-for-the-bigchain"></span><h1>Standard serialization for the bigchain<a class="headerlink" href="#standard-serialization-for-the-bigchain" title="Permalink to this headline">¶</a></h1>
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<p>After looking at this further I think that the python json module is still the best bet because it
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complies with the RFC. We can specify the encoding, separators used and enforce it to order by the keys to
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make sure that we obtain maximum interopelability.</p>
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<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">json</span>
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<span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="n">skipkeys</span><span class="o">=</span><span class="bp">False</span><span class="p">,</span> <span class="n">ensure_ascii</span><span class="o">=</span><span class="bp">False</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s2">"utf-8"</span><span class="p">,</span>
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<span class="n">separators</span><span class="o">=</span><span class="p">(</span><span class="s1">','</span><span class="p">,</span> <span class="s1">':'</span><span class="p">),</span> <span class="n">sort_keys</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li><code class="docutils literal"><span class="pre">skipkeys</span></code>: With skipkeys <code class="docutils literal"><span class="pre">False</span></code> if the provided keys are not a string the serialization will fail. This way we
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enforce all keys to be strings</li>
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<li><code class="docutils literal"><span class="pre">ensure_ascii</span></code>: The RFC recommends <code class="docutils literal"><span class="pre">utf-8</span></code> for maximum interoperability. By setting ensure_ascii to <code class="docutils literal"><span class="pre">False</span></code> we
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allow unicode characters and force the encoding to <code class="docutils literal"><span class="pre">utf-8</span></code>.</li>
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<li><code class="docutils literal"><span class="pre">separators</span></code>: We need to define a standard separator to use in the serialization. We did not do this different
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implementations could use different separators for serialization resulting in a still valid transaction but with
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a different hash e. g. an extra whitespace introduced in the serialization would not still create a valid json object
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but the hash would be different</li>
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</ul>
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<div class="section" id="example">
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<span id="id2"></span><h2>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2>
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<p>Everytime we need to perform some operation on the data like calculating the hash or signing/verifying the transaction
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we need to use the previous criteria to serialize the data and then use the <code class="docutils literal"><span class="pre">byte</span></code> representation of the serialized
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data (if we threat the data as bytes we eliminate possible enconding errors e.g. unicode characters)</p>
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<div class="highlight-python"><div class="highlight"><pre><span class="c1"># calculate the hash of a transaction</span>
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<span class="c1"># the transaction is a dictionary</span>
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<span class="n">tx_serialized</span> <span class="o">=</span> <span class="nb">bytes</span><span class="p">(</span><span class="n">serialize</span><span class="p">(</span><span class="n">tx</span><span class="p">))</span>
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<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">tx_serialized</span><span class="p">)</span><span class="o">.</span><span class="n">hexdigest</span><span class="p">()</span>
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<span class="c1"># signing a transaction</span>
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<span class="n">tx_serialized</span> <span class="o">=</span> <span class="nb">bytes</span><span class="p">(</span><span class="n">serialize</span><span class="p">(</span><span class="n">tx</span><span class="p">))</span>
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<span class="n">signature</span> <span class="o">=</span> <span class="n">sk</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">tx_serialized</span><span class="p">)</span>
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<span class="c1"># verify signature</span>
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<span class="n">tx_serialized</span> <span class="o">=</span> <span class="nb">bytes</span><span class="p">(</span><span class="n">serialize</span><span class="p">(</span><span class="n">tx</span><span class="p">))</span>
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<span class="n">vk</span><span class="o">.</span><span class="n">verify</span><span class="p">(</span><span class="n">signature</span><span class="p">,</span> <span class="n">tx_serialized</span><span class="p">)</span>
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</pre></div>
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<li><a class="reference internal" href="#">Example</a></li>
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<li><a class="reference internal" href="#example">Example</a></li>
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<li><a class="reference internal" href="#standard-serialization-for-the-bigchain">Standard serialization for the bigchain</a><ul>
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<li><a class="reference internal" href="#example">Example</a></li>
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