Summary - Security

Combine hash, HMAC and AES to write an encryptor.

Summary - Security

In this group you saw the security tools: hash with MessageDigest, HMAC with Mac, AES with Cipher, cryptographic random with SecureRandom and PBKDF2 with SecretKeyFactory.

This lesson includes a small task that combines three of them: you will hash a text with SHA-256, convert it to hex and print its length. This pattern brings together the foundation of security tools.

Exercise Summary: SHA-256 hex length

In main take val md = MessageDigest.getInstance("SHA-256"), hash with val bytes = md.digest("hello".toByteArray()). Convert to hex with val hex = bytes.joinToString("") { "%02x".format(it) } and print println(hex.length).

Show example solution

import java.security.MessageDigest

fun main() {
    val md = MessageDigest.getInstance("SHA-256")
    val bytes = md.digest("hello".toByteArray())
    val hex = bytes.joinToString("") { "%02x".format(it) }
    println(hex.length)
}

Test yourself

Which tool verifies integrity one-way?
- MessageDigest
- Cipher
- SecureRandom
- Mac
Show answer

MessageDigest — MessageDigest produces one-way hash.
Match the security tools

MessageDigest

Hash
Mac

HMAC
Cipher

AES encryption
SecretKeyFactory

PBKDF2

Complete the joinToString hex length

val hex = bytes.joinToString("") { "%02x".format(it) }
println(hex.____)

Show answer

val hex = bytes.joinToString("") { "%02x".format(it) }
println(hex.length)

Next lesson: Project design

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