Objective-C

Manually Duplicate SetSecretKeyViaPassword

Demonstrates how to duplicate the password string to binary secret key computation of SetSecretKeyViaPassword.

This is a cryptographically weak way of generating a secret key from a password. The SetSecretKeyViaPassword method is deprecated and should not be used.

Objective-C

#import <CkoCrypt2.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

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

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

//  The password string is transformed to a binary secret key by computing the 
//  MD5 digest (of the utf-8 password) to obtain 16 bytes.  
//  If the KeyLength is greater than 16 bytes, then the MD5 digest of the Base64 encoding 
//  of the utf-8 password is added.  A max of 32 bytes of key material is generated, and 
//  this is truncated to the actual KeyLength required.

crypt.CryptAlgorithm = @"aes";
crypt.KeyLength = [NSNumber numberWithInt:256];

NSString *password = @"this is my password";
[crypt SetSecretKeyViaPassword: password];

//  Examine the resulting SecretKey in hex:
NSLog(@"%@%@",@"Computed Secret Key = ",[crypt GetEncodedKey: @"hex"]);

//  Now perform the same computation manually:
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];

crypt.HashAlgorithm = @"md5";
crypt.Charset = @"utf-8";
crypt.EncodingMode = @"hex";
[sb Append: [crypt HashStringENC: password]];

NSString *passwordBase64 = [crypt EncodeString: password charset: @"utf-8" encoding: @"base64"];
[sb Append: [crypt HashStringENC: passwordBase64]];

NSLog(@"%@%@",@"Manually Computed = ",[sb GetAsString]);

//  The output is:
//  Computed Secret Key = 210D53992DFF432EC1B1A9698AF9DA16C7E90518F90E24828F78EC9E0A413B36
//  Manually Computed = 210D53992DFF432EC1B1A9698AF9DA16C7E90518F90E24828F78EC9E0A413B36