(Objective-C) Create PKCS1 RSA Signature with PEM Private Key

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#import <CkoPrivateKey.h>
#import <NSString.h>
#import <CkoRsa.h>

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

CkoPrivateKey *pkey = [[CkoPrivateKey alloc] init];

// Load the private key from an RSA PEM file:
BOOL success = [pkey LoadPemFile: @"pvkey2_rsa.pem"];

NSString *pkeyXml = 0;
// Get the private key in XML format:
pkeyXml = [pkey GetXml];

CkoRsa *rsa = [[CkoRsa alloc] init];

// Import the private key into the RSA object:
success = [rsa ImportPrivateKey: pkeyXml];
if (success != YES) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// Get the signature as hex.
rsa.EncodingMode = @"hex";

NSString *strData = @"This is the string to be signed.";

// Sign the string using the sha-1 hash algorithm.
// Other valid choices are "md2", "md5", "sha256",
// "sha384", and "sha512".
NSString *hexSig = [rsa SignStringENC: strData hashAlg: @"sha-1"];

NSLog(@"%@",hexSig);

NSLog(@"%@",@"Success!");