Hashing in iOS – Understand the basic concept

Hashing is a one-way process that transforms data into a fixed-length string that represents the original input. Unlike encryption, hashing is irreversible — you can’t decode the hashed result back to the original data.

import CryptoKit

func hash(_ input: String) -> String {
    let inputData = Data(input.utf8) // Line 1
    let hashed = SHA256.hash(data: inputData) // Line 2
    return hashed.map { String(format: "%02x", $0) }.joined() // Line 3
}

let originalPassword = "MySecret123"
let hashedPassword = hash(originalPassword) 
storeInDB(hashedPassword) // store this in database

import CryptoKit

func hash(_ input: String) -> String {
    let inputData = Data(input.utf8) // Line 1
    let hashed = SHA256.hash(data: inputData) // Line 2
    return hashed.map { String(format: "%02x", $0) }.joined() // Line 3
}

let originalPassword = "MySecret123"
let hashedPassword = hash(originalPassword) 
storeInDB(hashedPassword) // store this in database

Lets crack the hashing method!

Line 1: let inputData = Data(input.utf8)

• Converts the input string into a sequence of bytes (UTF-8 encoded).
• This is necessary because the SHA256 function works on binary data — not text.
  Example : "hello" becomes: [104, 101, 108, 108, 111]

Line 2: let hashed = SHA256.hash(data: inputData)

• Uses Swift’s CryptoKit framework to compute the SHA-256 hash of the input data.
• SHA256.hash(...) returns a Digest object containing the hashed bytes.

Line 3: hashed.map { String(format: "%02x", $0) }.joined()

• Then each byte of the hash converts into a 2-digit hex string (e.g., 185 → "b9").
• The map transforms each byte, and joined() combines them into one long string.
  Hurray! And the final result would look like :

2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

Example: Verifying a Password Using Hashing

Step 1: Hash the original password and store it

let originalPassword = "MySecret123"
let hashedPassword = hash(originalPassword) // The above hash() method
storeInDB(hashedPassword) // Save to database

let originalPassword = "MySecret123"
let hashedPassword = hash(originalPassword) // The above hash() method
storeInDB(hashedPassword) // Save to database

Step 2: When user logs in, hash their input and compare

let enteredPassword = "MySecret123"
let enteredHash = hash(enteredPassword) // The above hash() method
let storedHash = getHashFromDB()

if enteredHash == storedHash {
    print("✅ Password matched")
} else {
    print("❌ Incorrect password")
}

let enteredPassword = "MySecret123"
let enteredHash = hash(enteredPassword) // The above hash() method
let storedHash = getHashFromDB()

if enteredHash == storedHash {
    print("✅ Password matched")
} else {
    print("❌ Incorrect password")
}

❗ Hashing ≠ Encryption