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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>13.11 Cryptographic Hashing</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">The Racket Reference</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewselflink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Operations</a></td></tr><tr><td align="right">18 </td><td><a href="running.html" c
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returns the hash as a byte string with 20 bytes, 28 bytes, or 32
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bytes, respectively.</div></p><p>The <span class="RktVar">start</span> and <span class="RktVar">end</span> arguments determine the range of
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bytes of the input that are used to compute the hash. An <span class="RktVar">end</span>
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value of <span class="RktVal">#f</span> corresponds to the end of the byte string or an
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end-of-file position for an input port. When <span class="RktVar">in</span> is a byte
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string, the <span class="RktVar">start</span> and <span class="RktVar">end</span> values (when non
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<span class="RktVal">#f</span>) must be no greater than the length of the byte string,
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and <span class="RktVar">start</span> must be no greater than <span class="RktVar">end</span>. When
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<span class="RktVar">in</span> is an input port, <span class="RktVar">start</span> must be no greater than
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<span class="RktVar">end</span>; if <span class="RktVar">in</span> supplies less than <span class="RktVar">start</span> or
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<span class="RktVar">end</span> bytes before an end-of-file, then <span class="RktVar">start</span> and/or
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<span class="RktVar">end</span> is effectively changed to the number of supplied bytes
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(so that an empty or truncated byte sequence is hashed). When
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<span class="RktVar">in</span> is an input port and <span class="RktVar">end</span> is a number, then at
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most <span class="RktVar">end</span> bytes are read from the input port.</p><p>For security purposes, favor <span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha224-bytes%29%29" class="RktValLink" data-pltdoc="x">sha224-bytes</a></span> and
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<span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha256-bytes%29%29" class="RktValLink" data-pltdoc="x">sha256-bytes</a></span> (which are part of the SHA-2 family) over
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<span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha1-bytes%29%29" class="RktValLink" data-pltdoc="x">sha1-bytes</a></span>.</p><p>Use <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=file&rel=sha1b.html%23%2528def._%2528%2528lib._file%252Fsha1..rkt%2529._bytes-%7E3ehex-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">bytes->hex-string</a></span> from <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=file&rel=sha1b.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">file/sha1</span></a> to
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convert a byte string hash to a human-readable string.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha1-bytes%29%29" class="RktValLink" data-pltdoc="x">sha1-bytes</a></span><span class="hspace"> </span><span class="RktVal">#"abc"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#"\251\231>6G\6\201j\272>%qxP\302l\234\320\330\235"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktSym">file/sha1</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=file&rel=sha1b.html%23%2528def._%2528%2528lib._file%252Fsha1..rkt%2529._bytes-%7E3ehex-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">bytes->hex-string</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha1-bytes%29%29" class="RktValLink" data-pltdoc="x">sha1-bytes</a></span><span class="hspace"> </span><span class="RktVal">#"abc"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"a9993e364706816aba3e25717850c26c9cd0d89d"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=file&rel=sha1b.html%23%2528def._%2528%2528lib._file%252Fsha1..rkt%2529._bytes-%7E3ehex-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">bytes->hex-string</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha224-bytes%29%29" class="RktValLink" data-pltdoc="x">sha224-bytes</a></span><span class="hspace"> </span><span class="RktVal">#"abc"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=file&rel=sha1b.html%23%2528def._%2528%2528lib._file%252Fsha1..rkt%2529._bytes-%7E3ehex-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">bytes->hex-string</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="sha.html#%28def._%28%28quote._~23~25kernel%29._sha224-bytes%29%29" class="RktValLink" data-pltdoc="x">sha224-bytes</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span><span class="hspace"> </span><span class="RktVal">"xabcy"</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">4</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7"</span></p></td></tr></table></blockquote></div></p><p class="SHistory">Added in version 7.0.0.5 of package <span class="stt">base</span>.</p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" id="searchbox" type="text" tabi
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