Create PKCS1 RSA Signature with PEM Private Key

Demonstrates how to load a private key from a PEM file and create a PKCS1 RSA digital signature.

Download: Chilkat Cocoa Objective-C Libraries

NSMutableString *strOutput = [NSMutableString stringWithCapacity:1000];

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

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

BOOL success;

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

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

//  Any string argument automatically begins the 30-day trial.

success = [rsa UnlockComponent: @"30-day trial"];
if (success != YES) {
    [strOutput appendString: @"RSA component unlock failed"];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

//  Import the private key into the RSA component:
success = [rsa ImportPrivateKey: pkeyXml];
if (success != YES) {
    [strOutput appendString: rsa.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

//  This example will sign a string, and receive the signature
//  in a hex-encoded string.  Therefore, set the encoding mode
//  to "hex":
rsa.EncodingMode = @"hex";

//  If some other non-Chilkat software is going to verify
//  the signature, it is important to match the byte-ordering.
//  The LittleEndian property may be set to YES
//  for little-endian byte ordering,
//  or NO  for big-endian byte ordering.
//  Microsoft apps typically use little-endian, while
//  OpenSSL and other services (such as Amazon CloudFront)
//  use big-endian.
rsa.LittleEndian = NO;

NSString *strData;
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;
hexSig = [rsa SignStringENC: strData hashAlg: @"sha-1"];

[strOutput appendString: hexSig];
[strOutput appendString: @"\n"];

[strOutput appendString: @"Success!"];
[strOutput appendString: @"\n"];

self.mainTextField.stringValue = strOutput;