how to generate public/private key pair with like below in ios, swift

问题

This is how I generate public/private key pair

var statusCode: OSStatus
var publicKey: SecKey?
var privateKey: SecKey?

let publicKeyAttribute: [NSObject : NSObject] = [kSecAttrIsPermanent: true as NSObject, kSecAttrApplicationTag: "publictag".data(using: String.Encoding.utf8)! as NSObject]

let privateKeyAtrribute: [NSObject: NSObject] = [kSecAttrIsPermanent: true as NSObject, kSecAttrApplicationTag: "privatetag".data(using: String.Encoding.utf8)! as NSObject]

var keyPairAttr = [NSObject: Any]()
keyPairAttr[kSecAttrType] = kSecAttrKeyTypeRSA
keyPairAttr[kSecAttrKeySizeInBits] = 2048
keyPairAttr[kSecReturnData] = true
keyPairAttr[kSecPublicKeyAttrs] = publicKeyAttribute
keyPairAttr[kSecPrivateKeyAttrs] = privateKeyAtrribute


statusCode = SecKeyGeneratePair(keyPairAttr as CFDictionary, &publicKey, &privateKey)

This generates key pair like below,

Public key :

Optional(<SecKeyRef algorithm id: 1, key type: RSAPublicKey, version: 4, block size: 2048 bits, exponent: {hex: 10001, decimal: 65537}, modulus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addr: 0x60800002e580>)

Private key :

Optional(<SecKeyRef algorithm id: 1, key type: RSAPrivateKey, version: 4, block size: 2048 bits, addr: 0x60800002e5c0>)

What are these .pem or .der

But I need it like below

public key :

how to do it. hope your help with this.

回答1:

You can create public/private key pair using below method generateKeyPair and then use SecKeyCopyExternalRepresentation method for external representation.

Swift3

//tuple type for public/private key pair at class level
typealias KeyPair = (publicKey: SecKey, privateKey: SecKey)

// In your code block

    let publicKeyTag: String = "com.org.yourapp.publickey"
    let privateKeyTag: String = "com.org.yourapp.privatekey"
    let keyPair = generateKeyPair(publicKeyTag, privateTag: privateKeyTag, keySize: 2048)
    var pbError:Unmanaged<CFError>?
    var prError:Unmanaged<CFError>?
    guard let pbData = SecKeyCopyExternalRepresentation((keyPair?.publicKey)!, &pbError) as Data? else {
        print("error: ", pbError!.takeRetainedValue() as Error)
        return
    }
    guard let prData = SecKeyCopyExternalRepresentation((keyPair?.privateKey)!, &prError) as Data? else {
        print("private key error: ")
        return
    }
    let strPublicKey = appendPrefixSuffixTo(pbData.base64EncodedString(options: .lineLength64Characters), prefix: "-----BEGIN RSA PUBLIC KEY-----\n", suffix: "\n-----END RSA PUBLIC KEY-----")
    print("public key: \n", strPublicKey)

    let strPrivateKey = appendPrefixSuffixTo(prData.base64EncodedString(options: .lineLength64Characters), prefix: "-----BEGIN RSA PRIVATE KEY-----\n", suffix: "\n-----END RSA PRIVATE KEY-----")
    print("private key: \n", strPrivateKey)

Helper function:

func appendPrefixSuffixTo(_ string: String, prefix: String, suffix: String) -> String {
    return "\(prefix)\(string)\(suffix)"
}

generateKeyPair method returning the public/private KeyPair

func generateKeyPair(_ publicTag: String, privateTag: String, keySize: Int) -> KeyPair? {
    var sanityCheck: OSStatus = noErr
    var publicKey: SecKey?
    var privateKey: SecKey?
    // Container dictionaries
    var privateKeyAttr = [AnyHashable : Any]()
    var publicKeyAttr = [AnyHashable: Any]()
    var keyPairAttr = [AnyHashable : Any]()
    // Set top level dictionary for the keypair
    keyPairAttr[(kSecAttrKeyType ) as AnyHashable] = (kSecAttrKeyTypeRSA as Any)
    keyPairAttr[(kSecAttrKeySizeInBits as AnyHashable)] = Int(keySize)
    // Set private key dictionary
    privateKeyAttr[(kSecAttrIsPermanent as AnyHashable)] = Int(true)
    privateKeyAttr[(kSecAttrApplicationTag as AnyHashable)] = privateTag
    // Set public key dictionary.
    publicKeyAttr[(kSecAttrIsPermanent as AnyHashable)] = Int(true)
    publicKeyAttr[(kSecAttrApplicationTag as AnyHashable)] = publicTag

    keyPairAttr[(kSecPrivateKeyAttrs as AnyHashable)] = privateKeyAttr
    keyPairAttr[(kSecPublicKeyAttrs as AnyHashable)] = publicKeyAttr
    sanityCheck = SecKeyGeneratePair((keyPairAttr as CFDictionary), &publicKey, &privateKey)
    if sanityCheck == noErr && publicKey != nil && privateKey != nil {
        print("RSA key pair generation Successful")
        return KeyPair(publicKey: publicKey!, privateKey: privateKey!)
    }
    return nil
}

Output as below:

public key: 
-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEAz1zfbybUt5jZX5P6ymy+g04wj3iTYCV8eGbkFyqFNsfN8Lnk6x4x
zstfnpE6asV6NkBecQnT1a9X6AVxA4Mxq4CeysR10TRr8HGczQGKl7R3Nbvvmgw+
jX8LZGxsQTO6qYWhMAtOPFfsMW9iy3AsDE7OIYfya6y/l919ExbgPzJ+0nLdiBmd
bmmzOQ1PaKt3OcxG6qZyBoixRTTOm4UDCLDzYdjz5dS1rbvb7pD15TpkZBkuMRm5
QDv+xhKcz1UFGQP7ssZS++ZoQlF2CZJuLz8R1uUYg4xQnF0r1IBBrlVtKnblgMcA
ZykNweGwrdPaWF3PeZmbvG+/m+Kt7/4BJwIDAQAB
-----END RSA PUBLIC KEY-----

来源：https://stackoverflow.com/questions/45914097/how-to-generate-public-private-key-pair-with-like-below-in-ios-swift

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ios

swift

rsa

pem

der