How can I convert a String to an MD5 hash in iOS using Swift?

Solution 1:

There are two steps:
1. Create md5 data from a string
2. Covert the md5 data to a hex string

Swift 2.0:

func md5(string string: String) -> String {
    var digest = [UInt8](count: Int(CC_MD5_DIGEST_LENGTH), repeatedValue: 0)
    if let data = string.dataUsingEncoding(NSUTF8StringEncoding) {
        CC_MD5(data.bytes, CC_LONG(data.length), &digest)
    }

    var digestHex = ""
    for index in 0..<Int(CC_MD5_DIGEST_LENGTH) {
        digestHex += String(format: "%02x", digest[index])
    }

    return digestHex
}

//Test:
let digest = md5(string:"Hello")
print("digest: \(digest)")

Output:

digest: 8b1a9953c4611296a827abf8c47804d7

Swift 3.0:

func MD5(string: String) -> Data {
    let messageData = string.data(using:.utf8)!
    var digestData = Data(count: Int(CC_MD5_DIGEST_LENGTH))

    _ = digestData.withUnsafeMutableBytes {digestBytes in
        messageData.withUnsafeBytes {messageBytes in
            CC_MD5(messageBytes, CC_LONG(messageData.count), digestBytes)
        }
    }

    return digestData
}

//Test:
let md5Data = MD5(string:"Hello")

let md5Hex =  md5Data.map { String(format: "%02hhx", $0) }.joined()
print("md5Hex: \(md5Hex)")

let md5Base64 = md5Data.base64EncodedString()
print("md5Base64: \(md5Base64)")

Output:

md5Hex: 8b1a9953c4611296a827abf8c47804d7
md5Base64: ixqZU8RhEpaoJ6v4xHgE1w==

Swift 5.0:

import Foundation
import var CommonCrypto.CC_MD5_DIGEST_LENGTH
import func CommonCrypto.CC_MD5
import typealias CommonCrypto.CC_LONG

func MD5(string: String) -> Data {
        let length = Int(CC_MD5_DIGEST_LENGTH)
        let messageData = string.data(using:.utf8)!
        var digestData = Data(count: length)

        _ = digestData.withUnsafeMutableBytes { digestBytes -> UInt8 in
            messageData.withUnsafeBytes { messageBytes -> UInt8 in
                if let messageBytesBaseAddress = messageBytes.baseAddress, let digestBytesBlindMemory = digestBytes.bindMemory(to: UInt8.self).baseAddress {
                    let messageLength = CC_LONG(messageData.count)
                    CC_MD5(messageBytesBaseAddress, messageLength, digestBytesBlindMemory)
                }
                return 0
            }
        }
        return digestData
    }

//Test:
let md5Data = MD5(string:"Hello")

let md5Hex =  md5Data.map { String(format: "%02hhx", $0) }.joined()
print("md5Hex: \(md5Hex)")

let md5Base64 = md5Data.base64EncodedString()
print("md5Base64: \(md5Base64)")

Output:

md5Hex: 8b1a9953c4611296a827abf8c47804d7
md5Base64: ixqZU8RhEpaoJ6v4xHgE1w==

Notes:
#import <CommonCrypto/CommonCrypto.h> must be added to a Bridging-Header file

For how to create a Bridging-Header see this SO answer.

In general MD5 should not be used for new work, SHA256 is a current best practice.

Example from deprecated documentation section:

MD2, MD4, MD5, SHA1, SHA224, SHA256, SHA384, SHA512 (Swift 3+)

These functions will hash either String or Data input with one of eight cryptographic hash algorithms.

The name parameter specifies the hash function name as a String
Supported functions are MD2, MD4, MD5, SHA1, SHA224, SHA256, SHA384 and SHA512 a This example requires Common Crypto
It is necessary to have a bridging header to the project:
#import <CommonCrypto/CommonCrypto.h>
Add the Security.framework to the project.

This function takes a hash name and String to be hashed and returns a Data:

name: A name of a hash function as a String  
string: The String to be hashed  
returns: the hashed result as Data  

func hash(name:String, string:String) -> Data? {
    let data = string.data(using:.utf8)!
    return hash(name:name, data:data)
}

Examples:

let clearString = "clearData0123456"
let clearData   = clearString.data(using:.utf8)!
print("clearString: \(clearString)")
print("clearData: \(clearData as NSData)")

let hashSHA256 = hash(name:"SHA256", string:clearString)
print("hashSHA256: \(hashSHA256! as NSData)")

let hashMD5 = hash(name:"MD5", data:clearData)
print("hashMD5: \(hashMD5! as NSData)")

Output:

clearString: clearData0123456
clearData: <636c6561 72446174 61303132 33343536>

hashSHA256: <aabc766b 6b357564 e41f4f91 2d494bcc bfa16924 b574abbd ba9e3e9d a0c8920a>
hashMD5: <4df665f7 b94aea69 695b0e7b baf9e9d6>

Solution 2:

As of iOS 13 Apple has added the CryptoKit framework so you no longer need to import CommonCrypto or deal with its C API:

import Foundation
import CryptoKit

func MD5(string: String) -> String {
    let digest = Insecure.MD5.hash(data: string.data(using: .utf8) ?? Data())

    return digest.map {
        String(format: "%02hhx", $0)
    }.joined()
}

Solution 3:

After reading through the other answers on here (and needing to support other hash types as well) I wrote a String extension that handles multiple hash types and output types.

NOTE: CommonCrypto is included in Xcode 10, so you can simply import CommonCrypto without having to mess with a bridging header if you have the latest Xcode version installed... Otherwise a bridging header is necessary.

UPDATE: Both Swift 4 & 5 use the same String+Crypto.swift file below.

There is a separate Data+Crypto.swift file for Swift 5 (see below) as the api for 'withUnsafeMutableBytes' and 'withUnsafeBytes' changed between Swift 4 & 5.

String+Crypto.swift -- (for both Swift 4 & 5)

import Foundation
import CommonCrypto

// Defines types of hash string outputs available
public enum HashOutputType {
    // standard hex string output
    case hex
    // base 64 encoded string output
    case base64
}

// Defines types of hash algorithms available
public enum HashType {
    case md5
    case sha1
    case sha224
    case sha256
    case sha384
    case sha512

    var length: Int32 {
        switch self {
        case .md5: return CC_MD5_DIGEST_LENGTH
        case .sha1: return CC_SHA1_DIGEST_LENGTH
        case .sha224: return CC_SHA224_DIGEST_LENGTH
        case .sha256: return CC_SHA256_DIGEST_LENGTH
        case .sha384: return CC_SHA384_DIGEST_LENGTH
        case .sha512: return CC_SHA512_DIGEST_LENGTH
        }
    }
}

public extension String {

    /// Hashing algorithm for hashing a string instance.
    ///
    /// - Parameters:
    ///   - type: The type of hash to use.
    ///   - output: The type of output desired, defaults to .hex.
    /// - Returns: The requested hash output or nil if failure.
    public func hashed(_ type: HashType, output: HashOutputType = .hex) -> String? {

        // convert string to utf8 encoded data
        guard let message = data(using: .utf8) else { return nil }
        return message.hashed(type, output: output)
    } 
}

SWIFT 5 -- Data+Crypto.swift

import Foundation
import CommonCrypto

extension Data {

    /// Hashing algorithm that prepends an RSA2048ASN1Header to the beginning of the data being hashed.
    ///
    /// - Parameters:
    ///   - type: The type of hash algorithm to use for the hashing operation.
    ///   - output: The type of output string desired.
    /// - Returns: A hash string using the specified hashing algorithm, or nil.
    public func hashWithRSA2048Asn1Header(_ type: HashType, output: HashOutputType = .hex) -> String? {

        let rsa2048Asn1Header:[UInt8] = [
            0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
            0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00
        ]

        var headerData = Data(rsa2048Asn1Header)
        headerData.append(self)

        return hashed(type, output: output)
    }

    /// Hashing algorithm for hashing a Data instance.
    ///
    /// - Parameters:
    ///   - type: The type of hash to use.
    ///   - output: The type of hash output desired, defaults to .hex.
    ///   - Returns: The requested hash output or nil if failure.
    public func hashed(_ type: HashType, output: HashOutputType = .hex) -> String? {

        // setup data variable to hold hashed value
        var digest = Data(count: Int(type.length))

        _ = digest.withUnsafeMutableBytes{ digestBytes -> UInt8 in
            self.withUnsafeBytes { messageBytes -> UInt8 in
                if let mb = messageBytes.baseAddress, let db = digestBytes.bindMemory(to: UInt8.self).baseAddress {
                    let length = CC_LONG(self.count)
                    switch type {
                    case .md5: CC_MD5(mb, length, db)
                    case .sha1: CC_SHA1(mb, length, db)
                    case .sha224: CC_SHA224(mb, length, db)
                    case .sha256: CC_SHA256(mb, length, db)
                    case .sha384: CC_SHA384(mb, length, db)
                    case .sha512: CC_SHA512(mb, length, db)
                    }
                }
                return 0
            }
        }

        // return the value based on the specified output type.
        switch output {
        case .hex: return digest.map { String(format: "%02hhx", $0) }.joined()
        case .base64: return digest.base64EncodedString()
        }
    }
}

SWIFT 4 -- Data+Crypto.swift

import Foundation
import CommonCrypto 

extension Data {

    /// Hashing algorithm that prepends an RSA2048ASN1Header to the beginning of the data being hashed.
    ///
    /// - Parameters:
    ///   - type: The type of hash algorithm to use for the hashing operation.
    ///   - output: The type of output string desired.
    /// - Returns: A hash string using the specified hashing algorithm, or nil.
    public func hashWithRSA2048Asn1Header(_ type: HashType, output: HashOutputType = .hex) -> String? {

        let rsa2048Asn1Header:[UInt8] = [
            0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
            0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00
        ]

        var headerData = Data(bytes: rsa2048Asn1Header)
        headerData.append(self)

        return hashed(type, output: output)
    }

    /// Hashing algorithm for hashing a Data instance.
    ///
    /// - Parameters:
    ///   - type: The type of hash to use.
    ///   - output: The type of hash output desired, defaults to .hex.
    ///   - Returns: The requested hash output or nil if failure.
    public func hashed(_ type: HashType, output: HashOutputType = .hex) -> String? {

        // setup data variable to hold hashed value
        var digest = Data(count: Int(type.length))

        // generate hash using specified hash type
        _ = digest.withUnsafeMutableBytes { (digestBytes: UnsafeMutablePointer<UInt8>) in
            self.withUnsafeBytes { (messageBytes: UnsafePointer<UInt8>) in
                let length = CC_LONG(self.count)
                switch type {
                case .md5: CC_MD5(messageBytes, length, digestBytes)
                case .sha1: CC_SHA1(messageBytes, length, digestBytes)
                case .sha224: CC_SHA224(messageBytes, length, digestBytes)
                case .sha256: CC_SHA256(messageBytes, length, digestBytes)
                case .sha384: CC_SHA384(messageBytes, length, digestBytes)
                case .sha512: CC_SHA512(messageBytes, length, digestBytes)
                }
            }
        }

        // return the value based on the specified output type.
        switch output {
        case .hex: return digest.map { String(format: "%02hhx", $0) }.joined()
        case .base64: return digest.base64EncodedString()
        }
    }
}

Edit: since the hash actually happens on the Data, I split the hashing algorithm out into a Data extension. This allows the same algorithm to be used for SSL Certificate pinning hash operations as well.

Here's a short example of how you might use it for an SSL Pinning operation:

// Certificate pinning - get certificate as data
let data: Data = SecCertificateCopyData(serverCertificate) as Data

// compare hash of server certificate with local (expected) hash value
guard let serverHash = data.hashWithRSA2048Asn1Header(.sha256, output: .base64), serverHash == storedHash else {
    print("SSL PINNING: Server certificate hash does not match specified hash value.")
    return false
}

back to the original answer

I tested the hash algorithms using this:

let value = "This is my string"

if let md5 = value.hashed(.md5) {
    print("md5: \(md5)")
}
if let sha1 = value.hashed(.sha1) {
    print("sha1: \(sha1)")
}
if let sha224 = value.hashed(.sha224) {
    print("sha224: \(sha224)")
}
if let sha256 = value.hashed(.sha256) {
    print("sha256: \(sha256)")
}
if let sha384 = value.hashed(.sha384) {
    print("sha384: \(sha384)")
}
if let sha512 = value.hashed(.sha512) {
    print("sha512: \(sha512)")
}

and this is the printed results:

md5: c2a9ce57e8df081b4baad80d81868bbb
sha1: 37fb219bf98bee51d2fdc3ba6d866c97f06c8223
sha224: f88e2f20aa89fb4dffb6bdc62d7bd75e1ba02574fae4a437c3bf49c7
sha256: 9da6c02379110815278b615f015f0b254fd3d5a691c9d8abf8141655982c046b
sha384: d9d7fc8aefe7f8f0a969b132a59070836397147338e454acc6e65ca616099d03a61fcf9cc8c4d45a2623145ebd398450
sha512: 349cc35836ba85915ace9d7f895b712fe018452bb4b20ff257257e12adeb1e83ad780c6568a12d03f5b2cb1e3da23b8b7ced9012a188ef3855e0a8f3db211883

Solution 4:

SWIFT 3 version of md5 function:

func md5(_ string: String) -> String {

    let context = UnsafeMutablePointer<CC_MD5_CTX>.allocate(capacity: 1)
    var digest = Array<UInt8>(repeating:0, count:Int(CC_MD5_DIGEST_LENGTH))
    CC_MD5_Init(context)
    CC_MD5_Update(context, string, CC_LONG(string.lengthOfBytes(using: String.Encoding.utf8)))
    CC_MD5_Final(&digest, context)
    context.deallocate(capacity: 1)
    var hexString = ""
    for byte in digest {
        hexString += String(format:"%02x", byte)
    }

    return hexString
}

Original link from http://iosdeveloperzone.com