Objective-C

JWE with DEFLATE Compression

See more JSON Web Encryption (JWE) Examples

Demonstrates how to DEFLATE ("zip") compress the JWE payload prior to encryption.

Note: This example requires Chilkat v9.5.0.66 or greater.

Objective-C

#import <CkoStringBuilder.h>
#import <NSString.h>
#import <CkoJwe.h>
#import <CkoJsonObject.h>

BOOL success = NO;

// 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.

// Create some plaintext to be encrypted.
// This example will demonstrate with and without DEFLATE (zip) compression.
CkoStringBuilder *sbPlainText = [[CkoStringBuilder alloc] init];
BOOL bCrLf = YES;
NSString *line = @"Live long and prosper.";
[sbPlainText AppendLine: line crlf: bCrLf];
[sbPlainText AppendLine: line crlf: bCrLf];
[sbPlainText AppendLine: line crlf: bCrLf];
[sbPlainText AppendLine: line crlf: bCrLf];

// The text to be encrypted:
NSLog(@"%@",[sbPlainText GetAsString]);

CkoJwe *jwe = [[CkoJwe alloc] init];

// Build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256","zip":"DEF"}
// The "zip":"DEF" parameter indicates that the plaintext payload should
// be compressed prior to encryption.
CkoJsonObject *jweProtHdr = [[CkoJsonObject alloc] init];
[jweProtHdr AppendString: @"alg" value: @"A128KW"];
[jweProtHdr AppendString: @"enc" value: @"A128CBC-HS256"];
[jweProtHdr AppendString: @"zip" value: @"DEF"];
[jwe SetProtectedHeader: jweProtHdr];

// Set the AES key wrap key:
NSString *aesWrappingKey = @"GawgguFyGrWKav7AX4VKUg";
[jwe SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

// Encrypt and return the JWE in sbJweCompressed:
CkoStringBuilder *sbJweCompressed = [[CkoStringBuilder alloc] init];
success = [jwe EncryptSb: sbPlainText charset: @"utf-8" jweSb: sbJweCompressed];
if (success != YES) {
    NSLog(@"%@",jwe.LastErrorText);
    return;
}

// Show the compressed JWE:
NSLog(@"%@",[sbJweCompressed GetAsString]);
NSLog(@"%@%d",@"size of compressed JWE: ",[sbJweCompressed.Length intValue]);

// Now create a JWE without compression.
[jweProtHdr Delete: @"zip"];
// Make sure to update the shared protected header:
[jwe SetProtectedHeader: jweProtHdr];

CkoStringBuilder *sbJweUncompressed = [[CkoStringBuilder alloc] init];
success = [jwe EncryptSb: sbPlainText charset: @"utf-8" jweSb: sbJweUncompressed];
if (success != YES) {
    NSLog(@"%@",jwe.LastErrorText);
    return;
}

// Show the uncompressed JWE:
NSLog(@"%@",[sbJweUncompressed GetAsString]);
NSLog(@"%@%d",@"size of uncompressed JWE: ",[sbJweUncompressed.Length intValue]);

// Decrypting is the same whether compression is used or not.
// The "zip" header in the JWE indicates that the payload should be 
// automatically decompressed (inflated) after decrypting.
CkoJwe *jwe2 = [[CkoJwe alloc] init];
success = [jwe2 LoadJweSb: sbJweCompressed];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

// Set the AES wrap key.
[jwe2 SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

// Decrypt (also automatically decompresses).
CkoStringBuilder *sbOriginalText = [[CkoStringBuilder alloc] init];
success = [jwe2 DecryptSb: [NSNumber numberWithInt: 0] charset: @"utf-8" contentSb: sbOriginalText];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

NSLog(@"%@",@"original text from compressed JWE: ");
NSLog(@"%@",[sbOriginalText GetAsString]);

// -----------------------------------------------------------
// Do the same with the uncompressed JWE

success = [jwe2 LoadJweSb: sbJweUncompressed];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

// Set the AES wrap key.
[jwe2 SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

// Decrypt.
[sbOriginalText Clear];
success = [jwe2 DecryptSb: [NSNumber numberWithInt: 0] charset: @"utf-8" contentSb: sbOriginalText];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

NSLog(@"%@",@"original text from uncompressed JWE: ");
NSLog(@"%@",[sbOriginalText GetAsString]);

// ------------------------------------------------
// The output of this example is:
// (Note: Your output data will be different because the content encryption key is randomly generated.)

// eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2IiwiemlwIjoiREVGIn0.xuW-pEAIdEUFnk10m8ocursvktO8Of9ByCCAt6LgKkkOtCWCUn1kQw.zpGj-9WVni3cQxyOuZbcGA.0hzP1myua3oYpUHwCIY_3edBUREbUpLaX6wYuJduOdI.Ppc6aEO3y3B8BJ1FKMPjlA
// size of compressed JWE: 212
// eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.N4KeyC7nnSFkieJOyE24_zKeuV_m7v5UKoJb1TgV4Yc_r2RzUPNvyA.6AEdyXSCKx-iMmUJyypSLg.QpixfyrwhGpmwUDp623viik4smPav7vwPLiC2r-V-jwnSfEH3mxWu6DbrIz3mixaqATwynmEBzVPxvS9jTXpSAGCnniib4_0WoPl3r_wF5tlsKOEe--jpNso-DKd1Tp8jJxj3JkFWt3IRnUUKGj17g.sBfDwFc5fzpaI-UW8-SW4g
// size of uncompressed JWE: 303
// original text from compressed JWE: 
// Live long and prosper.
// Live long and prosper.
// Live long and prosper.
// Live long and prosper.
// 
// original text from uncompressed JWE: 
// Live long and prosper.
// Live long and prosper.
// Live long and prosper.
// Live long and prosper.
//