How to use ECC in iOS

Question

Is there any example for use ECC in iOS?

I noticed that the kSecAttrKeyTypeEC in Apple Developer Documents, but I can\'t use it to generic Key pair.

Below co

Answer 1

NSDictionary *parameters = @{
                             (__bridge id)kSecAttrKeyType: (__bridge id)kSecAttrKeyTypeEC,
                             (__bridge id)kSecAttrKeySizeInBits: @256,
                             (__bridge id)kSecPrivateKeyAttrs: @{
                                     (__bridge id)kSecAttrIsPermanent: @YES,
                                     (__bridge id)kSecAttrApplicationTag: [@"my.key.tag" dataUsingEncoding:NSUTF8StringEncoding],
                                     },
                             (__bridge id)kSecPublicKeyAttrs: @{
                                     (__bridge id)kSecAttrIsPermanent: @YES,
                                     (__bridge id)kSecAttrApplicationTag: [@"my.key.pubtag" dataUsingEncoding:NSUTF8StringEncoding],
                                     }
                             };

SecKeyRef publicKey, privateKey;
OSStatus status = SecKeyGeneratePair((__bridge CFDictionaryRef)parameters, &publicKey, &privateKey);

This works, double check your key size parameter.

Just a note, currently EC keys can only be used for signing/verifying data. Encryption/decryption returns errSecUnimplemented = -4.

Answer 2

CryptoKit now supports Ed25519 in iOS13+

https://developer.apple.com/documentation/cryptokit/curve25519/signing