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<TITLE>Encrypting a File or Stream with DES
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
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<B><A HREF="../javax.crypto/pkg.html">javax.crypto</A></B><font color="#666666" SIZE="-2">
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<B><A HREF="../javax.crypto/pkg.html#Encrypting%20and%20Decrypting">Encrypting and Decrypting</A></B><font color="#666666" SIZE="-2">
[6 examples]
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<h3>
e463.
Encrypting a File or Stream with DES</h3>
This example implements a class for encrypting and decrypting files or
streams using DES. The class is created with a key and can be used
repeatedly to encrypt and decrypt streams using that key.
<pre>
public class DesEncrypter {
Cipher ecipher;
Cipher dcipher;
DesEncrypter(SecretKey key) {
// Create an 8-byte initialization vector
byte[] iv = new byte[]{
(byte)<font color="#0066ff"><i>0x8E</i></font>, <font color="#0066ff"><i>0x12</i></font>, <font color="#0066ff"><i>0x39</i></font>, (byte)<font color="#0066ff"><i>0x9C</i></font>,
<font color="#0066ff"><i>0x07</i></font>, <font color="#0066ff"><i>0x72</i></font>, <font color="#0066ff"><i>0x6F</i></font>, <font color="#0066ff"><i>0x5A</i></font>
};
AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);
try {
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
// CBC requires an initialization vector
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
} catch (java.security.InvalidAlgorithmParameterException e) {
} catch (javax.crypto.NoSuchPaddingException e) {
} catch (java.security.NoSuchAlgorithmException e) {
} catch (java.security.InvalidKeyException e) {
}
}
// Buffer used to transport the bytes from one stream to another
byte[] buf = new byte[<font color="#0066ff"><i>1024</i></font>];
public void encrypt(InputStream in, OutputStream out) {
try {
// Bytes written to out will be encrypted
out = new CipherOutputStream(out, ecipher);
// Read in the cleartext bytes and write to out to encrypt
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
}
}
public void decrypt(InputStream in, OutputStream out) {
try {
// Bytes read from in will be decrypted
in = new CipherInputStream(in, dcipher);
// Read in the decrypted bytes and write the cleartext to out
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
}
}
}
</pre>
Here's an example that uses the class:
<pre>
try {
// Generate a temporary key. In practice, you would save this key.
// See also <a href="../javax.crypto/PassKey.html" class="eglink"><font size="-1"><b>e464</b> Encrypting with DES Using a Pass Phrase</font></a>.
SecretKey key = KeyGenerator.getInstance("DES").generateKey();
// Create encrypter/decrypter class
DesEncrypter encrypter = new DesEncrypter(key);
// Encrypt
encrypter.encrypt(new FileInputStream(<font color="#0066ff"><i>"cleartext1"</i></font>),
new FileOutputStream(<font color="#0066ff"><i>"ciphertext"</i></font>));
// Decrypt
encrypter.decrypt(new FileInputStream(<font color="#0066ff"><i>"ciphertext"</i></font>),
new FileOutputStream(<font color="#0066ff"><i>"cleartext2"</i></font>));
} catch (Exception e) {
}
</pre>
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Related Examples
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</table>
e461. <a class="eglink" href="ListCipher.html?l=rel">
Listing All Available Encryption and Decryption Algorithms
</a>
<br>
e462. <a class="eglink" href="DesString.html?l=rel">
Encrypting a String with DES
</a>
<br>
e464. <a class="eglink" href="PassKey.html?l=rel">
Encrypting with DES Using a Pass Phrase
</a>
<br>
e465. <a class="eglink" href="MakeDes.html?l=rel">
Converting a 56-bit Value to a DES Key
</a>
<br>
e466. <a class="eglink" href="EncryptObject.html?l=rel">
Encrypting an Object with DES
</a>
<br>
<table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
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<br>
See also:
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#Key%20Agreement">
Key Agreement
</a>
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#MAC">
MAC
</a>
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#Symmetric%20Keys">
Symmetric Keys
</a>
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