(Objective-C) RSASSA-PSS Algorithm with SHA256 Hashing

RSA encrypt a SHA256 hash with OAEP padding.

Note: This example requires Chilkat v11.0.0 or greater.

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

BOOL success = NO;

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

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

// Load the private key object from a PEM file.
// (To load from a PEM string, call LoadPem instead.)
success = [privkey LoadPemFile: @"somePath/myPrivateKey.pem"];
if (success == NO) {
    NSLog(@"%@",privkey.LastErrorText);
    return;
}

CkoRsa *rsa = [[CkoRsa alloc] init];
// Use RSA-PSS by setting PkcsPadding = NO
rsa.PkcsPadding = NO;
// Use SHA256
rsa.OaepHash = @"SHA-256";

[rsa UsePrivateKey: privkey];

// Generate a base64 signature.
rsa.EncodingMode = @"base64";

NSString *sigStr = [rsa SignStringENC: @"String to be signed" hashAlg: @"SHA-256"];
if (rsa.LastMethodSuccess == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

NSLog(@"%@%@",@"Signature: ",sigStr);