RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

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 LoadPkcs8EncryptedFile: @"raul_privateKey.key" password: @"a0123456789"];

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: @"Anything for 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";

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

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

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

//  Now verify with the public key.
//  This example shows how to use the public key from
//  a digital certificate (.cer file)
CkoCert *cert = [[[CkoCert alloc] init] autorelease];
success = [cert LoadFromFile: @"raul_publicKey.cer"];
if (success != YES) {
    [strOutput appendString: cert.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

CkoPublicKey *pubKey;
pubKey = [cert ExportPublicKey];

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

CkoRsa *rsa2 = [[[CkoRsa alloc] init] autorelease];
success = [rsa2 ImportPublicKey: pubKeyXml];
if (success != YES) {
    [strOutput appendString: rsa2.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

//  Verify the signature against the original data:
rsa2.EncodingMode = @"hex";
success = [rsa2 VerifyStringENC: strData hashAlg: @"sha-1" sig: hexSig];
if (success != YES) {
    [strOutput appendString: rsa2.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

[strOutput appendString: @"Signature verified!"];
[strOutput appendString: @"\n"];

//  Verify with incorrect data:
success = [rsa2 VerifyStringENC: @"something else" hashAlg: @"sha-1" sig: hexSig];
if (success != YES) {
    [strOutput appendString: ];
    [strOutput appendString: @"\n"];}


self.mainTextField.stringValue = strOutput;