B4X

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.

B4X

Dim success As Boolean = False

'  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.
Dim sbPlainText As ChilkatStringBuilder
sbPlainText.Initialize
Dim bCrLf As Boolean = True
Dim line As String = "Live long and prosper."
sbPlainText.AppendLine(line, bCrLf)
sbPlainText.AppendLine(line, bCrLf)
sbPlainText.AppendLine(line, bCrLf)
sbPlainText.AppendLine(line, bCrLf)

'  The text to be encrypted:
Log(sbPlainText.GetAsString)

Dim jwe As ChilkatJwe
jwe.Initialize

'  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.
Dim jweProtHdr As ChilkatJsonObject
jweProtHdr.Initialize
jweProtHdr.AppendString("alg", "A128KW")
jweProtHdr.AppendString("enc", "A128CBC-HS256")
jweProtHdr.AppendString("zip", "DEF")
jwe.SetProtectedHeader(jweProtHdr)

'  Set the AES key wrap key:
Dim aesWrappingKey As String = "GawgguFyGrWKav7AX4VKUg"
jwe.SetWrappingKey(0, aesWrappingKey, "base64url")

'  Encrypt and return the JWE in sbJweCompressed:
Dim sbJweCompressed As ChilkatStringBuilder
sbJweCompressed.Initialize
success = jwe.EncryptSb(sbPlainText, "utf-8", sbJweCompressed)
If success <> True Then
    Log(jwe.LastErrorText)
    Return
End If


'  Show the compressed JWE:
Log(sbJweCompressed.GetAsString)
Log("size of compressed JWE: " & sbJweCompressed.Length)

'  Now create a JWE without compression.
jweProtHdr.Delete("zip")
'  Make sure to update the shared protected header:
jwe.SetProtectedHeader(jweProtHdr)

Dim sbJweUncompressed As ChilkatStringBuilder
sbJweUncompressed.Initialize
success = jwe.EncryptSb(sbPlainText, "utf-8", sbJweUncompressed)
If success <> True Then
    Log(jwe.LastErrorText)
    Return
End If


'  Show the uncompressed JWE:
Log(sbJweUncompressed.GetAsString)
Log("size of uncompressed JWE: " & sbJweUncompressed.Length)

'  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.
Dim jwe2 As ChilkatJwe
jwe2.Initialize
success = jwe2.LoadJweSb(sbJweCompressed)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If

'  Set the AES wrap key.
jwe2.SetWrappingKey(0, aesWrappingKey, "base64url")

'  Decrypt (also automatically decompresses).
Dim sbOriginalText As ChilkatStringBuilder
sbOriginalText.Initialize
success = jwe2.DecryptSb(0, "utf-8", sbOriginalText)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If


Log("original text from compressed JWE: ")
Log(sbOriginalText.GetAsString)

'  -----------------------------------------------------------
'  Do the same with the uncompressed JWE

success = jwe2.LoadJweSb(sbJweUncompressed)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If

'  Set the AES wrap key.
jwe2.SetWrappingKey(0, aesWrappingKey, "base64url")

'  Decrypt.
sbOriginalText.Clear
success = jwe2.DecryptSb(0, "utf-8", sbOriginalText)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If


Log("original text from uncompressed JWE: ")
Log(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.
'