Kotlin - Blowfish Encryption and decryption Example

September 10, 2021

Blowfish is an encryption method developed by Bruce Schneier in 1993 as an alternative to the DES encryption method. It is significantly faster than DES and provides good encryption speed, although no effective cryptanalysis technique has been found to date. It is one of the first secure block ciphers that is not protected by any patents and is therefore freely available for anyone to use. This is a symmetric block cipher algorithm.

Block size: 64 bits
Key size: variable size from 32 to 448 bits
number of subsections: 18 [P-array]
number of rounds: 16
number of substitution blocks: 4 [each with 512 records of 32 bits each]develop

Example:

import java.io.UnsupportedEncodingException
import java.nio.charset.Charset
import java.security.InvalidKeyException
import java.security.NoSuchAlgorithmException
import java.util.*
import javax.crypto.BadPaddingException
import javax.crypto.Cipher
import javax.crypto.IllegalBlockSizeException
import javax.crypto.NoSuchPaddingException
import javax.crypto.spec.SecretKeySpec

/**
 * This program demonstrates how to 
 * encrypt/decrypt input using the Blowfish
 * Cipher with the Java Cryptograhpy.
 * */
class BlowfishKnowledgeFactory {
    @Throws(
        NoSuchAlgorithmException::class,
        NoSuchPaddingException::class,
        InvalidKeyException::class,
        IllegalBlockSizeException::class,
        BadPaddingException::class,
        UnsupportedEncodingException::class
    )
    fun encrypt(password: String, key: String): String {
        val KeyData = key.toByteArray()
        val KS = SecretKeySpec(KeyData, "Blowfish")
        val cipher = Cipher.getInstance("Blowfish")
        cipher.init(Cipher.ENCRYPT_MODE, KS)
        return Base64.getEncoder().encodeToString(cipher.
            doFinal(password.toByteArray(charset("UTF-8"))))
    }

    @Throws(
        NoSuchAlgorithmException::class,
        NoSuchPaddingException::class,
        InvalidKeyException::class,
        IllegalBlockSizeException::class,
        BadPaddingException::class
    )
    fun decrypt(encryptedtext: String?, key: String): String {
        val KeyData = key.toByteArray()
        val KS = SecretKeySpec(KeyData, "Blowfish")
        val ecryptedtexttobytes = Base64.getDecoder().
                   decode(encryptedtext)
        val cipher = Cipher.getInstance("Blowfish")
        cipher.init(Cipher.DECRYPT_MODE, KS)
        val decrypted = cipher.doFinal(ecryptedtexttobytes)
        return String(decrypted, Charset.forName("UTF-8"))
    }

    companion object {
        @Throws(Exception::class)
        @JvmStatic
        fun main(args: Array<String>) {
            val password = "Knf@123"
            val key = "knowledgefactory"
            println("Password: $password")
            val obj = BlowfishKnowledgeFactory()
            val enc_output = obj.encrypt(password, key)
            println("Encrypted text: $enc_output")
            val dec_output = obj.decrypt(enc_output, key)
            println("Decrypted text: $dec_output")
        }
    }
}

Output:

Password: Knf@123

Encrypted text: 4DTHqnctCuk=

Decrypted text: Knf@123

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