Using Collections and Strings in a Reusable Class - Java Programming: Comprehensive Concepts and Techniques - page 581

Figure 9-38
displays the
pseudocode that
outlines the logic for
the encrypt() method.
The encryption
method specified in
the requirements
document requires the
password to be cut in
half and the two halves
inverted. Then the
order of the characters
in the resulting string
is reversed (spelled
backward). Each char-
acter is compared with
the character in the
original string and
manipulated bitwise.
Finally, a hash code is computed for the original password and appended to the
encrypted one.
Figure 9-39 displays the code for the encrypt() method of the Password class.

encrypt() method (returns String: encrypted password; parameter String: password)

Begin

Obtain password length

Calculate midpoint of password

Encrypted password = last half of password (from midpoint to end)

+ first half of password (from beginning to midpoint, exclusive)

Reverse order of characters in encrypted password

Loop through all characters in the encrypted password

Set current character to a bitwise AND with corresponding original character

End loop

Compute hash code for original password

Append hash code to encrypted password

Return string value of encrypted password
End

FIGURE 9-38

221 // Encrypts original password returning new encrypted String

222 private String encrypt ( String pswd )

223 {

224 StringBuffer encryptPswd;

225 int pswdSize = 0;

226 int midpoint = 0;

227 int hashCode = 0;

228
229 // swap first and last half of password

230 pswdSize = pswd.length () ;

231 midpoint = pswdSize/2;

232 encryptPswd = new StringBuffer ( pswd.substring ( midpoint ) // get last half of pswd

233 + pswd.substring ( 0,midpoint )) ; // and concatenate first

half

234
235 encryptPswd.reverse () ; // reverses order of characters in password

236
237 for ( int i=0; i < pswdSize; ++i ) // encrypt each character

238 encryptPswd.setCharAt ( i, ( char )( encryptPswd.charAt ( i ) & pswd.charAt ( i )) ) ;

239
240 hashCode = pswd.hashCode () ; // hash code for original password

241 encryptPswd.append ( hashCode ) ;

242
243 return encryptPswd.toString () ;

244 }

245 }

FIGURE 9-39

The first step in the encryption algorithm implemented by the encrypt()
method is to exchange the first half of the password with the last half. As shown
in Figure 9-39, this is accomplished in code by obtaining the length of the string,
using the String length() method (line 230 of Figure 9-39) and then using