MD5 Generator

MD5Generator.kt

import java.security.MessageDigest
import java.security.NoSuchAlgorithmException

// Source - https://medium.com/@hayk.mkrtchyan8998/shedding-light-on-android-encryption-android-crypto-api-part-1-introduction-9623ca992dc2

// Our algorithm name. As there's no a predefined constant, we'll make our own :)
private const val MD5_ALGORITHM = "MD5"

// A String extension to generate a hash value
@Throws(NoSuchAlgorithmException::class, NullPointerException::class)
fun String.generateMD5Hash(): String {
    val md = MessageDigest.getInstance(MD5_ALGORITHM)
    val inputBytes: ByteArray = this.encodeToByteArray()
    val hashData: ByteArray = md.digest(inputBytes)

    return hashData.toHex()
}

// An extension to convert ByteArray to hexadecimal String representation
fun ByteArray.toHex(): String {
    return joinToString("") { "%02x".format(it) }
}

fun main() {
    // You can also use runCatching, but it will catch all the Exceptions.
    try {
        val inputText = "Let's encrypt this message with MD5"

        // You should apply error handling as this function may through an exception
        val hashValue = inputText.generateMD5Hash()
        println("#1 Generated hash is: $hashValue")

        val anotherInput = "Completely another message, could be song lyrics"
        val anotherHashValue = anotherInput.generateMD5Hash()
        println("#2 Generated hash is: $anotherHashValue")
    } catch (e: NoSuchAlgorithmException) {
        // In case an incorrect algorithm is passed or the algorithm is not supported
        e.printStackTrace()
    } catch (e: NullPointerException) {
        // Just try passing null in MessageDigest.getInstance()
        e.printStackTrace()
    }
}