Objective-C

Generate ECDSA Key and Get Details as XML

See more ECC Examples

Demonstrates how to generate an ECDSA key and gets the parts as XML. Objective-C

#import <CkoEcc.h>
#import <CkoPrng.h>
#import <NSString.h>
#import <CkoPrivateKey.h>
#import <CkoAsn.h>
#import <CkoXml.h>
#import <CkoCrypt2.h>

BOOL success = NO;

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoEcc *ecc = [[CkoEcc alloc] init];

// Generate a random ECC private key on the secp256k1 curve.
// Chilkat also supports other curves, such as secp384r1, secp521r1, and secp256r1.

// Create a Fortuna PRNG and seed it with system entropy.
// This will be our source of random data for generating the ECC private key.
CkoPrng *fortuna = [[CkoPrng alloc] init];
NSString *entropy = [fortuna GetEntropy: [NSNumber numberWithInt: 32] encoding: @"base64"];
success = [fortuna AddEntropy: entropy encoding: @"base64"];

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [ecc GenKey: @"secp256k1" prng: fortuna privKey: privKey];
if (success == NO) {
    NSLog(@"%@",ecc.LastErrorText);
    return;
}

// An EC private key has this ASN.1
// ECPrivateKey ::= SEQUENCE {
//     version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
//     privateKey     OCTET STRING,
//     parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
//     publicKey  [1] BIT STRING OPTIONAL (This is the ANSI X9.63 public key format.)

CkoAsn *asn = [[CkoAsn alloc] init];
success = [asn LoadEncoded: [privKey GetPkcs1ENC: @"base64"] encoding: @"base64"];
if (success != YES) {
    NSLog(@"%@",asn.LastErrorText);
    return;
}

CkoXml *xml = [[CkoXml alloc] init];
[xml LoadXml: [asn AsnToXml]];

NSLog(@"%@",[xml GetXml]);

// The XML looks like this:
// <?xml version="1.0" encoding="utf-8" ?>
// <sequence>
//     <int>01</int>
//     <octets>JgJvBG+3wletkJab8iXAkpz0O8/AgWZSpkYVcB7SpnU=</octets>
//     <contextSpecific tag="0" constructed="1">
//         <oid>1.3.132.0.10</oid>
//     </contextSpecific>
// </sequence>

// The 32-byte private key is in the octets..
// Get it as hex.
CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
NSString *privKeyHex = [crypt ReEncode: [xml GetChildContent: @"octets"] fromEncoding: @"base64" toEncoding: @"hex"];

NSLog(@"%@%@",@"EC private key as hex = ",privKeyHex);