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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN""http://www.w3.org/TR/REC-html40/frameset.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc on Thu Apr 27 23:36:03 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Class SecureRandom</TITLE><LINK REL ="stylesheet" TYPE="text/css" HREF="../../stylesheet.css" TITLE="Style"></HEAD><BODY BGCOLOR="white"><!-- ========== START OF NAVBAR ========== --><A NAME="navbar_top"><!-- --></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/SecureRandom.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup> 2 Platform<br>Std. Ed. v1.3</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../java/security/SecureClassLoader.html"><B>PREV CLASS</B></A> <A HREF="../../java/security/SecureRandomSpi.html"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../index.html" TARGET="_top"><B>FRAMES</B></A> <A HREF="SecureRandom.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: INNER | FIELD | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: FIELD | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><!-- =========== END OF NAVBAR =========== --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">java.security</FONT><BR>Class SecureRandom</H2><PRE><A HREF="../../java/lang/Object.html">java.lang.Object</A> | +--<A HREF="../../java/util/Random.html">java.util.Random</A> | +--<B>java.security.SecureRandom</B></PRE><DL><DT><B>All Implemented Interfaces:</B> <DD><A HREF="../../java/io/Serializable.html">Serializable</A></DD></DL><HR><DL><DT>public class <B>SecureRandom</B><DT>extends <A HREF="../../java/util/Random.html">Random</A></DL><P><p>This class provides a cryptographically strong pseudo-random number generator (PRNG). <p>Like other algorithm-based classes in Java Security, SecureRandom provides implementation-independent algorithms, whereby a caller (application code) requests a particular PRNG algorithm and is handed back a SecureRandom object for that algorithm. It is also possible, if desired, to request a particular algorithm from a particular provider. See the <code>getInstance</code> methods. <p>Thus, there are two ways to request a SecureRandom object: by specifying either just an algorithm name, or both an algorithm name and a package provider. <ul> <li>If just an algorithm name is specified, as in: <pre> SecureRandom random = SecureRandom.getInstance("SHA1PRNG"); </pre> the system will determine if there is an implementation of the algorithm requested available in the environment, and if there is more than one, if there is a preferred one.<p> <li>If both an algorithm name and a package provider are specified, as in: <pre> SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN"); </pre> the system will determine if there is an implementation of the algorithm in the package requested, and throw an exception if there is not. </ul> <p>The SecureRandom implementation attempts to completely randomize the internal state of the generator itself unless the caller follows the call to a <code>getInstance</code> method with a call to the <code>setSeed</code> method: <pre> SecureRandom random = SecureRandom.getInstance("SHA1PRNG"); random.setSeed(seed); </pre> <p>After the caller obtains the SecureRandom object from the <code>getInstance</code> call, it can call <code>nextBytes</code> to generate random bytes: <pre> byte bytes[] = new byte[20]; random.nextBytes(bytes); </pre> <p>The caller may also invoke the <code>generateSeed</code> method to generate a given number of seed bytes (to seed other random number generators, for example): <pre> byte seed[] = random.generateSeed(20); </pre><P><DL><DT><B>See Also: </B><DD><A HREF="../../java/security/SecureRandomSpi.html"><CODE>SecureRandomSpi</CODE></A>, <A HREF="../../java/util/Random.html"><CODE>Random</CODE></A>, <A HREF="../../serialized-form.html#java.security.SecureRandom">Serialized Form</A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> </CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#SecureRandom()">SecureRandom</A></B>()</CODE><BR> By using this constructor, the caller obtains a SecureRandom object containing the implementation from the highest-priority installed provider that has a SecureRandom implementation.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> </CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#SecureRandom(byte[])">SecureRandom</A></B>(byte[] seed)</CODE><BR> By using this constructor, the caller obtains a SecureRandom object containing the implementation from the highest-priority installed provider that has a SecureRandom implementation.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected </CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#SecureRandom(java.security.SecureRandomSpi, java.security.Provider)">SecureRandom</A></B>(<A HREF="../../java/security/SecureRandomSpi.html">SecureRandomSpi</A> secureRandomSpi, <A HREF="../../java/security/Provider.html">Provider</A> provider)</CODE><BR> Creates a SecureRandom object.</TD></TR></TABLE> <!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> byte[]</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#generateSeed(int)">generateSeed</A></B>(int numBytes)</CODE><BR> Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static <A HREF="../../java/security/SecureRandom.html">SecureRandom</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#getInstance(java.lang.String)">getInstance</A></B>(<A HREF="../../java/lang/String.html">String</A> algorithm)</CODE><BR> Generates a SecureRandom object that implements the specified Pseudo Random Number Generator (PRNG) algorithm.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static <A HREF="../../java/security/SecureRandom.html">SecureRandom</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#getInstance(java.lang.String, java.lang.String)">getInstance</A></B>(<A HREF="../../java/lang/String.html">String</A> algorithm, <A HREF="../../java/lang/String.html">String</A> provider)</CODE><BR> Generates a SecureRandom object for the specified PRNG algorithm, as supplied from the specified provider, if such a PRNG implementation is available from the provider.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/security/Provider.html">Provider</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#getProvider()">getProvider</A></B>()</CODE><BR> Returns the provider of this SecureRandom object.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static byte[]</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#getSeed(int)">getSeed</A></B>(int numBytes)</CODE><BR> Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected int</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#next(int)">next</A></B>(int numBits)</CODE><BR> Generates an integer containing the user-specified number of pseudo-random bits (right justified, with leading zeros).</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#nextBytes(byte[])">nextBytes</A></B>(byte[] bytes)</CODE><BR> Generates a user-specified number of random bytes.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#setSeed(byte[])">setSeed</A></B>(byte[] seed)</CODE><BR> Reseeds this random object.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/SecureRandom.html#setSeed(long)">setSeed</A></B>(long seed)</CODE><BR> Reseeds this random object, using the eight bytes contained in the given <code>long seed</code>.</TD></TR></TABLE> <A NAME="methods_inherited_from_class_java.util.Random"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Methods inherited from class java.util.<A HREF="../../java/util/Random.html">Random</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../java/util/Random.html#nextBoolean()">nextBoolean</A>, <A HREF="../../java/util/Random.html#nextDouble()">nextDouble</A>, <A HREF="../../java/util/Random.html#nextFloat()">nextFloat</A>, <A HREF="../../java/util/Random.html#nextGaussian()">nextGaussian</A>, <A HREF="../../java/util/Random.html#nextInt()">nextInt</A>, <A HREF="../../java/util/Random.html#nextInt(int)">nextInt</A>, <A HREF="../../java/util/Random.html#nextLong()">nextLong</A></CODE></TD></TR></TABLE> <A NAME="methods_inherited_from_class_java.lang.Object"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Methods inherited from class java.lang.<A HREF="../../java/lang/Object.html">Object</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../java/lang/Object.html#clone()">clone</A>, <A HREF="../../java/lang/Object.html#equals(java.lang.Object)">equals</A>, <A HREF="../../java/lang/Object.html#finalize()">finalize</A>, <A HREF="../../java/lang/Object.html#getClass()">getClass</A>, <A HREF="../../java/lang/Object.html#hashCode()">hashCode</A>, <A HREF="../../java/lang/Object.html#notify()">notify</A>, <A HREF="../../java/lang/Object.html#notifyAll()">notifyAll</A>, <A HREF="../../java/lang/Object.html#toString()">toString</A>, <A HREF="../../java/lang/Object.html#wait()">wait</A>, <A HREF="../../java/lang/Object.html#wait(long)">wait</A>, <A HREF="../../java/lang/Object.html#wait(long, int)">wait</A></CODE></TD></TR></TABLE> <P><!-- ============ FIELD DETAIL =========== -->⌨️ 快捷键说明
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