ServerCrypto

ServerCrypto is a library that makes server-side cryptography easy in Swift.

Installation

To use ServerCrypto in your project, add this line to your Package.swift:

.package(url: "https://github.com/alexaubry/ServerCrypto", from: "1.0.0")

Make sure you have OpenSSL installed before using the library.

On macOS, you need to provide the following flags to build or test from the command line:

swift build -Xswiftc -I/usr/local/opt/openssl/include -Xlinker -L/usr/local/opt/openssl/lib

Hashing

To compute the hash of a sequence of bytes, you use an instance of Hasher.

Hasher can generate hashes for Data, [UInt8] ; and any type than conforms to the Bytes protocols.

The following hashing algorithms are supported:

.md4 .md5 .sha1 .sha224 .sha256 .sha384 .sha512 .ripeMd160

Example

To compute the SHA-256 hash of a String, write the following code:

import Hash

let hasher = Hasher.sha256

let messageData = "Hello world".data(using: .utf8)!
let hashData = try hasher.makeHash(for: messageData) // Returns a Data object
let hashHexString = hashData.hexString

HMAC Signature

To create an HMAC signature, you need:

A message digest / hashing algorithm
A key with a password
A message to sign

You use an instance of Signer to generate an HMAC signature. Any type supported by Hasher is also supported by Signer.

Example

To compute the SHA-256 HMAC of a String, you need to follow these steps:

1- Create an HMAC key with a password

import Signature

let key = try HMACKey(password: "secret")

2- Create an HMAC signer

let signer = Signer.hmac(key)

3- Get the HMAC for the message

let messageData = "Hello world".data(using: .utf8)!
let hmacData = signer.sign(messageData, with: .sha256) // Returns a Data object
let hmacHexString = hmacData.hexString

HMAC Verification

To verify that an HMAC signature is valid for the message you expect, you need:

A message digest / hashing algorithm
A key with an expected password
An expected message
A signature to verify

You use an instance of Signer to verify an HMAC signature. The signature must be a Data object. The expected message can be any type supported by Hasher.

Example

To verify the SHA-256 HMAC of a String, you need to follow these steps:

1- Create an HMAC key with the expected password

import Signature

let key = try HMACKey(password: "secret")

2- Create an HMAC signer

let signer = Signer.hmac(key)

3- Verify the HMAC for the message

let hmacData = ...
let messageData = "Hello world".data(using: .utf8)!
let isValid = signer.verify(signature: hmacData, for: messageData, with: .sha256) // Returns a Bool

Asymmetric Signature

Signature.framework can generate signatures using private keys and algorithms like RSA and ECDSA.

To create a signature, you need:

A message digest / hashing algorithm
A private PEM-encoded key
A message to sign

You use an instance of Signer to generate a signature. Any type supported by Hasher is also supported by Signer.

Example

To compute the SHA-256 ECDSA signature of a String, you need to follow these steps:

1- Load a private key from a PEM file:

import Signature

let privateKey = try AsymmetricKey.makePrivateKey(readingPEMAtPath: "path/to/public/key.pem", passphrase: "...")

You can also load a PEM key from memory using AsymmetricKey.makePrivateKey(readingPEMData: Data,passphrase: String?).

2- Create an asymmetric signer

let signer = Signer.asymmetric(privateKey)

3- Get the signature for the message

let messageData = "Hello world".data(using: .utf8)!
let hmacData = signer.sign(messageData, with: .sha256) // Returns a Data object
let hmacHexString = hmacData.hexString

Asymmetric Signature Verification

To verify that a signature is valid for the message you expect, you need:

A message digest / hashing algorithm
The public key associated with the expected private key
An expected message
A signature to verify

You use an instance of Signer to verify a signature. The signature must be a Data object. The expected message can be any type supported by Hasher.

Example

To verify that a SHA-256 ECDSA signature of a String is valid for the public key, you need to follow these steps:

1- Load the public key from a PEM file

import Signature

let publicKey = try AsymmetricKey.makePublicKey(readingPEMAtPath: "path/to/private/key.pem")

You can also load the key from memory using AsymmetricKey.makePublicKey(readingPEMData: Data).

2- Create an asymmetric signer

let signer = Signer.asymmetric(publicKey)

3- Verify the signatrure for the message

let hmacData = ...
let messageData = "Hello world".data(using: .utf8)!
let isValid = signer.verify(signature: hmacData, for: messageData, with: .sha256) // Returns a Bool

Author

Alexis Aubry, me@alexaubry.fr

You can find me on Twitter : @_alexaubry

License

ServerCrypto is available under the MIT License. See the LICENSE file for more info.