Vigenère cipher: Difference between revisions

===Alternative Version===

<lang Java>

import com.google.common.collect.Streams;

import java.util.function.Supplier;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import static java.nio.charset.StandardCharsets.US_ASCII;

public class VigenereCipher {

private final static int LOWER = 'A';

private final static int UPPER = 'Z';

private final static int SIZE = UPPER - LOWER + 1;

private final Supplier<Stream<Character>> maskStream;

public VigenereCipher(final String key) {

final String mask = new String(key.getBytes(US_ASCII)).toUpperCase();

maskStream = () ->

Stream.iterate(0, i -> (i+1) % mask.length()).map(mask::charAt);

}

private String transform(final String text, final boolean encode) {

final Stream<Integer> textStream = text.toUpperCase().chars().boxed()

.filter(i -> i >= LOWER && i <= UPPER);

return Streams.zip(textStream, maskStream.get(), (c, m) ->

encode ? c + m - 2 * LOWER : c - m + SIZE)

.map(c -> Character.toString(c % SIZE + LOWER))

.collect(Collectors.joining());

}

public String encrypt(final String plaintext) {

return transform(plaintext,true);

}

public String decrypt(final String ciphertext) {

return transform(ciphertext,false);

}

}

import org.junit.jupiter.api.DisplayName;

import org.junit.jupiter.api.Test;

import java.net.URI;

import static org.junit.jupiter.api.Assertions.assertEquals;

class VigenereCipherTest {

private static final VigenereCipher Vigenere = new VigenereCipher("VIGENERECIPHER");

@Test

@DisplayName("encipher/decipher round-trip succeeds")

void vigenereCipherTest() {

final String input = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!";

final String expectEncrypted = "WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY";

final String expectDecrypted = "BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH";

final String ciphertext = Vigenere.encrypt(input);

assertEquals(expectEncrypted, ciphertext);

final String plaintext = Vigenere.decrypt(ciphertext);

assertEquals(expectDecrypted, plaintext);

}

}

</lang>