Как создать пару асимметричных ключей RSA в Swift для IOS?

Хороший пример того, как это сделать в Swift, есть в проекте CertificateSigningRequestSwift_Test на GitHub. Используя один вызов SecKeyCreateRandomKey(), можно одновременно сгенерировать пару открытого и закрытого ключей, и они будут сохранены в цепочке ключей.

        let tagPublic = "com.example.public"
        let tagPrivate = "com.example.private"

        let publicKeyParameters: [String: AnyObject] = [
            String(kSecAttrIsPermanent): kCFBooleanTrue,
            String(kSecAttrApplicationTag): tagPublic as AnyObject,
            String(kSecAttrAccessible): kSecAttrAccessibleAlways
        ]

        var privateKeyParameters: [String: AnyObject] = [
            String(kSecAttrIsPermanent): kCFBooleanTrue,
            String(kSecAttrApplicationTag): tagPrivate as AnyObject,
            String(kSecAttrAccessible): kSecAttrAccessibleAlways
        ]

        //Define what type of keys to be generated here
        var parameters: [String: AnyObject] = [
            String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
            String(kSecAttrKeySizeInBits): 2048,
            String(kSecReturnRef): kCFBooleanTrue,
            kSecPublicKeyAttrs as String: publicKeyParameters as AnyObject,
            kSecPrivateKeyAttrs as String: privateKeyParameters as AnyObject,
        ]

        //Use Apple Security Framework to generate keys, save them to application keychain
        var error: Unmanaged<CFError>?
        let privateKey = SecKeyCreateRandomKey(parameters as CFDictionary, &error)

        if privateKey == nil{
            print("Error creating keys occurred: \(error!.takeRetainedValue() as Error), keys weren't created")
            return
        }

        //Get generated public key
        let query: [String: AnyObject] = [
            String(kSecClass): kSecClassKey,
            String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
            String(kSecAttrApplicationTag): tagPublic as AnyObject,
            String(kSecReturnRef): kCFBooleanTrue
        ]

        var publicKeyReturn:AnyObject?

        let result = SecItemCopyMatching(query as CFDictionary, &publicKeyReturn)

        if result != errSecSuccess{
            print("Error getting publicKey from keychain occurred: \(result)")
            return
        }

        let publicKey = publicKeyReturn as! SecKey?

        //Set block size
        let keyBlockSize = SecKeyGetBlockSize(self.publicKey!)

        //Ask keychain to provide the publicKey in bits
        let query: [String: AnyObject] = [
            String(kSecClass): kSecClassKey,
            String(kSecAttrKeyType): keyAlgorithm.secKeyAttrType,
            String(kSecAttrApplicationTag): tagPublic as AnyObject,
            String(kSecReturnData): kCFBooleanTrue
        ]

        var tempPublicKeyBits:AnyObject?

        _ = SecItemCopyMatching(query as CFDictionary, &tempPublicKeyBits)

        guard let publicKeyBits = tempPublicKeyBits as? Data else {
            return
        }

Heimdall кажется тем, что вы ищете. Он прост в использовании, может создавать пары ключей RSA, шифровать, расшифровывать, подписывать и проверять.

Он использует цепочку для ключей iOS/OS X для хранения ключей, поэтому ключи хранятся безопасным образом.

Из файла Readme на GitHub:

if let heimdall = Heimdall(tagPrefix: "com.example") {
    let testString = "This is a test string"

    // Encryption/Decryption
    if let encryptedString = heimdall.encrypt(testString) {
        println(encryptedString) // "cQzaQCQLhAWqkDyPoHnPrpsVh..."

        if let decryptedString = heimdall.decrypt(encryptedString) {
            println(decryptedString) // "This is a test string"
        }
    }

    // Signatures/Verification
    if let signature = heimdall.sign(testString) {
        println(signature) // "fMVOFj6SQ7h+cZTEXZxkpgaDsMrki..."
        var verified = heimdall.verify(testString, signatureBase64: signature)
        println(verified) // True

        // If someone meddles with the message and the signature becomes invalid
        verified = heimdall.verify(testString + "injected false message",
                                    signatureBase64: signature)
        println(verified) // False
    }
}