Convert SecKeyRef to EC_KEY in iOS - ios

Question

I'm creating CSR from openSSL but due to OpenSSL isn't storing keys in secure enclave so I chooses objective C to create key pair (private key and public key) in secure enclave and send to OpenSSL for X509 certificate. I get successfully public key in NSData and then convert const unsigned char * bitsOfKeyDataPublicKey = (unsigned char *) [publicKey bytes]; and then create public key EC_KEY*_ec_keyPublic = d2i_EC_PUBKEY(NULL,&bitsOfKeyDataPublicKey, publicKeyLegnth);. But For Private key we get SecKeyRef from objective c so for creation EC_Key how can we convert private key or is this any way to convert or use private key ?
Looking for response.
Thanks

Answer 1

You can change private key from SecKeyRef to NSData
Example:
- (NSData *)getPrivateKeyBits {
OSStatus sanityCheck = noErr;
NSData * privateKeyBits = nil;
NSMutableDictionary * queryPrivateKey = [[NSMutableDictionary alloc] init];
// Set the public key query dictionary.
[queryPrivateKey setObject:(id)kSecClassKey forKey:(id)kSecClass];
[queryPrivateKey setObject:_privateTag forKey:(id)kSecAttrApplicationTag];
[queryPrivateKey setObject:(id)kSecAttrKeyTypeEC forKey:(id)kSecAttrKeyType];
[queryPrivateKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnData];
// Get the key bits.
sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)queryPrivateKey, (void *)&privateKeyBits);
if (sanityCheck != noErr) {
privateKeyBits = nil;
}
else if (sanityCheck == errSecItemNotFound) {
privateKeyBits = nil;
}
return privateKeyBits;
}
Don't forget to use the _privateTag used for generating private key
now you can use:
const unsigned char *bitsOfKeyDataPrivateKey = (unsigned char *) [[self getPrivateKeyBits] bytes];
EC_KEY *_ec_keyPrivate = d2i_EC_PUBKEY(NULL,&bitsOfKeyDataPrivateKey, privateKeyLegnth);