desstring.html
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<TITLE>Encrypting a String with DES
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
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<A HREF="../index.html">List of Packages</A>
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<B><A HREF="../javax.crypto/pkg.html">javax.crypto</A></B><font color="#666666" SIZE="-2">
[14 examples]
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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>
e462.
Encrypting a String with DES</h3>
This example implements a class for encrypting and decrypting strings
using DES. The class is created with a key and can be used repeatedly
to encrypt and decrypt strings using that key.
<pre>
public class DesEncrypter {
Cipher ecipher;
Cipher dcipher;
DesEncrypter(SecretKey key) {
try {
ecipher = Cipher.getInstance("DES");
dcipher = Cipher.getInstance("DES");
ecipher.init(Cipher.ENCRYPT_MODE, key);
dcipher.init(Cipher.DECRYPT_MODE, key);
} catch (javax.crypto.NoSuchPaddingException e) {
} catch (java.security.NoSuchAlgorithmException e) {
} catch (java.security.InvalidKeyException e) {
}
}
public String encrypt(String str) {
try {
// Encode the string into bytes using utf-8
byte[] utf8 = str.getBytes("UTF8");
// Encrypt
byte[] enc = ecipher.doFinal(utf8);
// Encode bytes to base64 to get a string
return new sun.misc.BASE64Encoder().encode(enc);
} catch (javax.crypto.BadPaddingException e) {
} catch (IllegalBlockSizeException e) {
} catch (UnsupportedEncodingException e) {
} catch (java.io.IOException e) {
}
return null;
}
public String decrypt(String str) {
try {
// Decode base64 to get bytes
byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
// Decrypt
byte[] utf8 = dcipher.doFinal(dec);
// Decode using utf-8
return new String(utf8, "UTF8");
} catch (javax.crypto.BadPaddingException e) {
} catch (IllegalBlockSizeException e) {
} catch (UnsupportedEncodingException e) {
} catch (java.io.IOException e) {
}
return null;
}
}
</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
String encrypted = encrypter.encrypt(<font color="#0066ff"><i>"Don't tell anybody!"</i></font>);
// Decrypt
String decrypted = encrypter.decrypt(encrypted);
} catch (Exception e) {
}
</pre>
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Related Examples
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e461. <a class="eglink" href="ListCipher.html?l=rel">
Listing All Available Encryption and Decryption Algorithms
</a>
<br>
e463. <a class="eglink" href="DesFile.html?l=rel">
Encrypting a File or Stream 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>
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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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