Objective-C

RSA Signature using Private Key from .snk File

See more RSA Examples

A .snk file (Strong Name Key file) is a file format used in the .NET ecosystem to store an RSA public/private key pair. This key pair is typically used for strong-naming assemblies, which is a process of signing .NET assemblies to ensure their integrity and to uniquely identify them.

This example loads a private key from a .snk file and creates an RSA signature.

Objective-C

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

BOOL success = NO;

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

//  Load the .snk and return the private key as XML.
NSString *xmlStr = [rsa SnkToXml: @"./test.snk"];
if (rsa.LastMethodSuccess == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [privKey LoadXml: xmlStr];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

success = [rsa UsePrivateKey: privKey];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

//  Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
//  Return the signature in base64 format.
rsa.EncodingMode = @"base64";
rsa.Charset = @"utf-8";
NSString *sigBase64 = [rsa SignStringENC: @"This is the text to be hashed and signed." hashAlg: @"sha256"];
if (rsa.LastMethodSuccess == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

NSLog(@"%@%@",@"RSA signature as base64: ",sigBase64);