Help with RSA signature

[Aleph72]

Hello,
I'm using this framework to generate the key pair and sign a message.
I'm creating the key pair with:
self.rsaKeyFactory = [[MIHRSAKeyFactory alloc] init];
self.rsaKeyFactory.preferedKeySize = MIHRSAKey1024;
self.keyPair = [self.rsaKeyFactory generateKeyPair];

and then sign with:
- (NSString *)signMessageData:(NSData *)data withKey:(MIHRSAPrivateKey *)privKey {
NSError *signingError = nil;
NSData *signatureData = [privKey signWithSHA256:data error:&signingError];
if (signingError != nil) {
NSLog(@"Error al firmar el mensaje: %@", signingError.localizedDescription);
}
NSString *signString = [signatureData MIH_base64EncodedString];
return signString;
}

For what I know, signing with a 1024 private key should give a 128byte signature, but I get just 86 bytes.
I've been told to generate a 128 bytes signature, so any help would be really apreciated.

Thanks.

[Aleph72]

I'll answer myself this time.
The problem was the line "NSString *signString = [signatureData MIH_base64EncodedString];"
signatureData is exactly 128 byte, so I changed the method to return directly the NSData instead of converting it back to a NSString.