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(Objective-C) JWE using PBES2 Key WrappingDemonstrates how to create and decrypt a JWE that using PBES2 key wrapping. This example demonstrates PBES2 with HMAC SHA-256 and A128KW wrapping. It is also possible to do the following by simply changing the "alg" parameter:
Note: This example requires Chilkat v9.5.0.66 or greater.
#import <NSString.h> #import <CkoJwe.h> #import <CkoJsonObject.h> #import <CkoPrng.h> // This requires the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. // Note: This example requires Chilkat v9.5.0.66 or greater. BOOL success; NSString *plaintext = @"Live long and prosper."; CkoJwe *jwe = [[CkoJwe alloc] init]; // First build the JWE Protected Header.. CkoJsonObject *jweProtHdr = [[CkoJsonObject alloc] init]; [jweProtHdr AppendString: @"alg" value: @"PBES2-HS256+A128KW"]; [jweProtHdr AppendString: @"enc" value: @"A128GCM"]; // PBES2 requires two additional parameters: // 1) A random salt parameter ("p2s") containing 8 or more bytes in base64url format. // 2) An iteration count parameter ("p2c"). A minimum count of 1000 is recommended. // The iteration count is intended to make the PBES2 computation more expensive (time consuming) // to prevent brute-force attacks. CkoPrng *prng = [[CkoPrng alloc] init]; [jweProtHdr AppendString: @"p2s" value: [prng GenRandom: [NSNumber numberWithInt: 16] encoding: @"base64url"]]; [jweProtHdr AppendString: @"p2c" value: @"1000"]; NSLog(@"%@%@",@"JWE Protected Header: ",[jweProtHdr Emit]); NSLog(@"%@",@"--"); // Don't forget to actually provide the protected header to the JWE object: [jwe SetProtectedHeader: jweProtHdr]; // Set the PBES2 password int recipientIndex = 0; [jwe SetPassword: [NSNumber numberWithInt: recipientIndex] password: @"top secret"]; // Encrypt and return the JWE: NSString *strJwe = [jwe Encrypt: plaintext charset: @"utf-8"]; if (jwe.LastMethodSuccess != YES) { NSLog(@"%@",jwe.LastErrorText); return; } // Show the JWE we just created: NSLog(@"%@",strJwe); // Decrypt the JWE. CkoJwe *jwe2 = [[CkoJwe alloc] init]; success = [jwe2 LoadJwe: strJwe]; if (success != YES) { NSLog(@"%@",jwe2.LastErrorText); return; } // Set the PBES2 password [jwe2 SetPassword: [NSNumber numberWithInt: recipientIndex] password: @"top secret"]; // Decrypt. NSString *originalPlaintext = [jwe2 Decrypt: [NSNumber numberWithInt: 0] charset: @"utf-8"]; if (jwe2.LastMethodSuccess != YES) { NSLog(@"%@",jwe2.LastErrorText); return; } NSLog(@"%@",@"original text: "); NSLog(@"%@",originalPlaintext); // Sample output: // JWE Protected Header: {"alg":"PBES2-HS256+A128KW","enc":"A128GCM","p2s":"z39rTEfRy1T1Yn_D1mZRlg","p2c":"1000"} // -- // eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMTI4R0NNIiwicDJzIjoiejM5clRFZlJ5MVQxWW5fRDFtWlJsZyIsInAyYyI6IjEwMDAifQ.koYt6PrFmYwcwdcT7ZcvXHA1d-Xez5h4.luGlbvEnZp-7IsBOj42Yhw.YMTcfLf8Qe4zazozGV2OAu3cUdQ8Kg.rWub47ESWkc6IqZJTvSTmg // original text: // Live long and prosper. |
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