程序代写代做 Java algorithm Assignment 1 - File Encryption - Submission

Assignment 1 – File Encryption – Submission
Please upload your Java source code file, FileEncryptor.java, along with a text file called Assignment1.txt containing the answers to the following questions:
1. For version 1 of the program, operating in ECB mode:
a) What did you notice about the ciphertext, and why do you think that was?
b) What did you notice about the size of the generated ciphertext files. Why was this?
2. For version 2 of the program, operating in CBC mode with default IV: a) What did you notice about the size of the generated ciphertext files?
b) How is the initialization vector being passed between encryption and decryption?
c) Is this particularly secure?
3. For version 3 of the program, operating in CBC mode with a random IV:
a) What did you notice about the size of the generated ciphertext files?
The upload dialog will only accept filetypes of .java and .txt – no Word documents
or PDF’s please!

FileEncryptorSkeleton.java6.2KB Text file
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
/**
* Program to encrypt and decrypt files using a key derived from a
password by PBKDF2
* and AES-128
*/
/**
* @author les
* @version $Revision: 1.1 $
*/
public class FileEncryptorSkeleton {
private static final String progName = “FileEncryptor”;
private static final int bufSize = 128;

/**
* @param args
*/
public static void main(String[] args) {
BufferedInputStream in = null;
buffered input stream to read from
BufferedOutputStream out = null;
buffered output stream to write to
SecretKeyFactory kf = null;
// Something to create a key for us
// A
// And a
KeySpec ks = null;
// This is how we specify what kind of key we want it to
generate
byte[] salt = new byte[20];
// Some salt for use with PBKDF2, only not very salty
SecretKey key = null;
// The key that it generates
Cipher cipher = null;
// The cipher that will do the real work
SecretKeySpec keyspec = null;
we pass the key to the Cipher
int bytesRead = 0;
// Number of bytes read into the input file buffer
// First, check the user has provided all the
required arguments, and if they haven’t, tell them then exit
if(args.length != 4) {
printUsageMessage(); System.exit(1);
}
// Open the input file
try {
in = new BufferedInputStream(new
FileInputStream(args[1]));
// How
” + args[1], null);
}
System.exit(1);
} catch (FileNotFoundException e) {
printErrorMessage(“Unable to open input file:
// And then the output file
try {

out = new BufferedOutputStream(new
FileOutputStream(args[2]));
} catch (FileNotFoundException e) {
printErrorMessage(“Unable to open output file:
” + args[2], e);
}
System.exit(1);
// Create a PBKDF2 secret key factory
// Set up a KeySpec for password-based key generation
of a 128-bit key
key
// Now run the passphrase through PBKDF2 to get the
// Get the byte encoded key value as a byte array
byte[] aeskey = key.getEncoded();
// Now generate a Cipher object for AES encryption in
ECBC mode with PKCS #5 padding
// Use ECB for the first task, then switch to CBC for
versions 2 and 3
try {
} catch (NoSuchAlgorithmException e) {
printErrorMessage(“No Such Algorithm Exception
when creating main cipher”, e);
System.exit(2);

} catch (NoSuchPaddingException e) {
printErrorMessage(“No Such Padding Exception
when creating main cipher”,e);
System.exit(2);
}
// Set a variable to indicate whether we’re in
encrypt or decrypt mode, based upon args[0]
int cipherMode = -1;
char mode = Character.toLowerCase(args[0].charAt(0));
switch (mode) {
case ‘e’ : cipherMode = Cipher.ENCRYPT_MODE;
case ‘d’ : cipherMode = Cipher.DECRYPT_MODE;
default: printUsageMessage(); System.exit(1);
}
// Set up a secret key specification, based on the
16-byte (128-bit) AES key array previously generated
// Now initialize the cipher in the right mode, with
the keyspec and the ivspec
try {
} catch (InvalidKeyException e) {
printErrorMessage(“Invalid Key Spec”,e);
} catch (InvalidAlgorithmParameterException e) {
printErrorMessage(“Invalid Algorithm
break;
break;
System.exit(2);
Parameter”, e); System.exit(2);
}
// Set up some input and output byte array buffers
byte[] inputBuffer = new byte[bufSize];
byte[] outputBuffer = null;
// “Prime the pump” – we’ve got to read something
before we can encrypt it
// and not encrypt anything if we read nothing.
try {
bytesRead = in.read(inputBuffer);
} catch (IOException e) {

printErrorMessage(“Error reading input file ”
+ args[1],e); System.exit(1);
}
// As long as we’ve read something, loop around
encrypting, writing and reading
// bytesRead will be zero if nothing was read, or -1
on EOF – treat them both the same
while (bytesRead > 0) {
// Now encrypt this block
// Write the generated block to file
try {
out.write(outputBuffer);
} catch (IOException e) {
printErrorMessage(“Error writing to
output file ” + args[2],e); System.exit(1);
}
// And read in the next block of the file
try {
bytesRead = in.read(inputBuffer);
} catch (IOException e) {
printErrorMessage(“Error reading input
file ” + args[1],e); System.exit(1);
} }
// Now do the final processing
// Write the final block of output
try {
out.write(outputBuffer);
} catch (IOException e) {

printErrorMessage(“Error on final write to
output file ” + args[2],e); System.exit(1);
}
// Close the output files
try {
in.close();
out.close();
} catch (IOException e) {
printErrorMessage(“Error closing file”, e);
}
// If we were continuing beyond this point, we should
really overwrite key material, drop KeySpecs, etc.
}
/**
* Print an error message on stderr, optionally picking up
additional detail from
* a passed exception
* @param errMsg
* @param e
*/
private static void printErrorMessage(String errMsg,
Exception e) {
}
System.err.println(errMsg);
if (e != null)
System.err.println(e.getMessage());
/**
* Print a usage message
*/
private static void printUsageMessage() {
System.out.println(progName + ” $Revision: 1.1 $:
Usage: ” + progName + ” E/D infile outfile passphrase”);
}
}

infile20.txt20.8KB Text file
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