192 lines
7.5 KiB
Plaintext
Generated
192 lines
7.5 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: SHA256 Hashes</title>
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<link rel=stylesheet href="site.css">
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<div class="example" id="sha256-hashes">
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<h2><a href="./">Go by Example</a>: SHA256 Hashes</h2>
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<table>
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<tr>
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<td class="docs">
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<p><a href="https://en.wikipedia.org/wiki/SHA-2"><em>SHA256 hashes</em></a> are
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frequently used to compute short identities for binary
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or text blobs. For example, TLS/SSL certificates use SHA256
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to compute a certificate’s signature. Here’s how to compute
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SHA256 hashes in Go.</p>
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</td>
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<td class="code empty leading">
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</td>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="https://go.dev/play/p/IHM1lZVm_Jm"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Go implements several hash functions in various
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<code>crypto/*</code> packages.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
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</span></span><span class="line"><span class="cl"> <span class="s">"crypto/sha256"</span>
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</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
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</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">s</span> <span class="o">:=</span> <span class="s">"sha256 this string"</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Here we start with a new hash.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">h</span> <span class="o">:=</span> <span class="nx">sha256</span><span class="p">.</span><span class="nf">New</span><span class="p">()</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>Write</code> expects bytes. If you have a string <code>s</code>,
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use <code>[]byte(s)</code> to coerce it to bytes.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">h</span><span class="p">.</span><span class="nf">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>This gets the finalized hash result as a byte
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slice. The argument to <code>Sum</code> can be used to append
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to an existing byte slice: it usually isn’t needed.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">bs</span> <span class="o">:=</span> <span class="nx">h</span><span class="p">.</span><span class="nf">Sum</span><span class="p">(</span><span class="kc">nil</span><span class="p">)</span></span></span></code></pre>
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</td>
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<td class="docs">
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<td class="code">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">s</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%x\n"</span><span class="p">,</span> <span class="nx">bs</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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<p>Running the program computes the hash and prints it in
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a human-readable hex format.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run sha256-hashes.go
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</span></span><span class="line"><span class="cl"><span class="go">sha256 this string
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</span></span></span><span class="line"><span class="cl"><span class="go">1af1dfa857bf1d8814fe1af8983c18080019922e557f15a8a...</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>You can compute other hashes using a similar pattern to
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the one shown above. For example, to compute
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SHA512 hashes import <code>crypto/sha512</code> and use
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<code>sha512.New()</code>.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Note that if you need cryptographically secure hashes,
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you should carefully research
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<a href="https://en.wikipedia.org/wiki/Cryptographic_hash_function">hash strength</a>!</p>
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</td>
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<td class="code empty">
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="base64-encoding">Base64 Encoding</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"crypto/sha256\"\u000A \"fmt\"\u000A)\u000A');codeLines.push('func main() {\u000A s :\u003D \"sha256 this string\"\u000A');codeLines.push(' h :\u003D sha256.New()\u000A');codeLines.push(' h.Write([]byte(s))\u000A');codeLines.push(' bs :\u003D h.Sum(nil)\u000A');codeLines.push(' fmt.Println(s)\u000A fmt.Printf(\"%x\\n\", bs)\u000A}\u000A');codeLines.push('');codeLines.push('');codeLines.push('');
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