I am developing an iOS app using swift 3.
I need to export an SecKey
(which is the user RSA publickey reference) to a string (e.g base64) in order to share it through a generated QRCode.
It also has to work the other way since the other user that scans the QRCode
, will be able to rebuild a SecKey
reference from the string extracted from the QRCode.
I found few tutorials but I don't understand exactly what I need to extract from the SecKey
reference, and I don't know how to convert it to a String
.
Export Key (iOS 10 only)
var error:Unmanaged<CFError>?
if let cfdata = SecKeyCopyExternalRepresentation(publicKey!, &error) {
let data:Data = cfdata as Data
let b64Key = data.base64EncodedString()
}
See https://stackoverflow.com/a/30662270/5276890 and https://stackoverflow.com/a/27935528/5276890 for longer ways which probably support iOS < 10.
Reimport Key
guard let data2 = Data.init(base64Encoded: b64Key) else {
return
}
let keyDict:[NSObject:NSObject] = [
kSecAttrKeyType: kSecAttrKeyTypeRSA,
kSecAttrKeyClass: kSecAttrKeyClassPublic,
kSecAttrKeySizeInBits: NSNumber(value: 512),
kSecReturnPersistentRef: true as NSObject
]
guard let publicKey = SecKeyCreateWithData(data2 as CFData, keyDict as CFDictionary, nil) else {
return
}
Note: This generates a base64 key and not a certificate. A lot of code samples online deal with how to generate a public key from a certificate using SecCertificateCreateWithData
Also: 512 bit is fast to generate but worthless. Pick a longer and secure value once you're satisfied with the results.
I got valid results back when importing the key I generated and exported, so I assume it works, but I did not try to encrypt and decrypt with it.