I am trying to generate public and private keys for an ECDH handshake.
Back end is using p256 for public key. I am getting a failed request with status 0
public func makeHandShake(completion: @escaping (Bool, String?) -> ()) {
guard let config = self.config else { completion(false,APP_CONFIG_ERROR)
return
}
var rData = HandshakeRequestTwo()
let sessionValue = AppUtils().generateSessionID()
rData.session = sessionValue
//generating my ECDH Key Pair
let sPrivateKey = P256.KeyAgreement.PrivateKey()
let sPublicKey = sPrivateKey.publicKey
let privateKeyBase64 = sPrivateKey.rawRepresentation.base64EncodedString()
print("My Private Key (Base64): \(privateKeyBase64)")
let publicKeyBase64 = sPublicKey.rawRepresentation.base64EncodedString()
print("My Public Key (Base64): \(publicKeyBase64)")
rData.value = sPublicKey.rawRepresentation.base64EncodedString()
let encoder = JSONEncoder()
do {
let jsonData = try encoder.encode(rData)
if let jsonString = String(data: jsonData, encoding: .utf8) {
print("Request Payload: \(jsonString)")
}
} catch {
print("Error encoding request model to JSON: \(error)")
completion(false, "Error encoding request model")
return
}
self.rsaReqResponseHandler(config: config, endpoint: config.services.handShake.endpoint, model: rData) { resToDecode, error in
print("Response received before guard : \(resToDecode ?? "No response")")
guard let responseString = resToDecode else {
print("response string is nil")
completion(false,error)
return
}
print("response received: \(responseString)")
let decoder = JSONDecoder()
do {
let request = try decoder.decode(DefaultResponseTwo.self, from: Data(responseString.utf8))
let msg = request.message
let status = request.status == 1 ? true : false
completion(status,msg)
guard let serverPublicKeyBase64 = request.data?.value else {
print("Server response is missing the value")
completion(false, config.messages.serviceError)
return
}
print("Server Public Key (Base64): \(serverPublicKeyBase64)")
if serverPublicKeyBase64.isEmpty {
print("Server public key is an empty string.")
completion(false, config.messages.serviceError)
return
}
guard let serverPublicKeyData = Data(base64Encoded: serverPublicKeyBase64) else {
print("Failed to decode server public key from Base64. Data is invalid.")
completion(false, config.messages.serviceError)
return
}
print("Decoded server public key data: \(serverPublicKeyData)")
guard let serverPublicKey = try? P256.KeyAgreement.PublicKey(rawRepresentation: serverPublicKeyData) else {
print("Decoded server public key data is invalid for P-256 format.")
completion(false, config.messages.serviceError)
return
}
// Derive Shared Secret and AES Key
let sSharedSecret = try sPrivateKey.sharedSecretFromKeyAgreement(with: serverPublicKey)
// Derive AES Key from Shared Secret
let symmetricKey = sSharedSecret.hkdfDerivedSymmetricKey(
using: SHA256.self,
salt: "AES".data(using: .utf8) ?? Data(),
sharedInfo: Data(),
outputByteCount: 32
)
// Storing AES Key in Config
let symmetricKeyBase64 = symmetricKey.withUnsafeBytes { Data($0) }.base64EncodedString()
print("Derived Key: \(symmetricKeyBase64)")
self.config?.cryptoConfig.key = symmetricKeyBase64
AppUtils.Log(from: self, with: "Handshake Successful, AES Key Established")
} catch {
AppUtils.Log(from: self, with: "Handshake Failed :: \(error)")
completion(false, self.config?.messages.serviceError)
}
}
} this is request struct model public struct HandshakeRequestTwo: Codable {
public var session: String?
public var value: String?
public enum CodingKeys: CodingKey {
case session
case value
}
public init(session: String? = nil, value: String? = nil) {
self.session = session
self.value = value
}
} This is backend's response {"message":"Success","status":1,"data":{"senderId":"POSTBANK","value":"MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAErLxbfQzX+xnYVT1LLP5VOKtkMRVPRCoqYHcCRTM64EMEOaRU16yzsN+2PZMJc0HpdKNegJQZMmswZtg6U9JGVw=="}} This is my response struct model public struct DefaultResponseTwo: Codable {
public var message: String?
public var status: Int?
public var data: HandshakeData?
public init(message: String? = nil, status: Int? = nil, data: HandshakeData? = nil) {
self.message = message
self.status = status
self.data = data
}
}
public struct HandshakeData: Codable {
public var senderId: String?
public var value: String?
public init(senderId: String? = nil, value: String? = nil) {
self.senderId = senderId
self.value = value
}
}
