Objective-C

Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

See more OpenSSL Examples

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

The in.dat file contains the original data that was signed, and can contain text or binary data of any type. The above OpenSSL command does the following:

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

Objective-C

#import <CkoPublicKey.h>
#import <CkoBinData.h>
#import <CkoRsa.h>

BOOL success = NO;

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

CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];

// Load the public key from an PEM file:
success = [pubKey LoadFromFile: @"pubKey.pem"];
if (success == NO) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

// Load the data of the original file that was signed.
CkoBinData *bdFileData = [[CkoBinData alloc] init];
success = [bdFileData LoadFile: @"in.dat"];

// Load the signature.
CkoBinData *bdSig = [[CkoBinData alloc] init];
success = [bdSig LoadFile: @"signature.sig"];

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

// Import the public key into the RSA component:
success = [rsa UsePublicKey: pubKey];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// OpenSSL uses big-endian.
rsa.LittleEndian = NO;

success = [rsa VerifyBd: bdFileData hashAlgorithm: @"sha256" bdSig: bdSig];
if (success != YES) {
    NSLog(@"%@",rsa.LastErrorText);
    NSLog(@"%@",@"The signature was invalid.");
    return;
}

NSLog(@"%@",@"The signature was verified.");