B4X

JWE using "dir" Direct use of Shared Symmetric Key

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

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.

Dim plaintext As String = "Live long and prosper."

Dim jwe As ChilkatJwe
jwe.Initialize

'  First build the JWE Protected Header..
Dim jweProtHdr As ChilkatJsonObject
jweProtHdr.Initialize
jweProtHdr.AppendString("alg", "dir")
jweProtHdr.AppendString("enc", "A128GCM")

'  Don't forget to actually provide the protected header to the JWE object:
jwe.SetProtectedHeader(jweProtHdr)

'  The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
'  Given that the "alg" = "dir", we are to directly specify the AES GCM key.
'  (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

'  Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

'  The SetWrappingKey method is also used for "dir" direct keys.
'  However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
'  which is specified by calling SetWrappingKey with an index of 0.

Dim recipientIndex As Int = 0
jwe.SetWrappingKey(recipientIndex, "000102030405060708090A0B0C0D0E0F", "hex")

'  Encrypt and return the JWE:
Dim strJwe As String = jwe.Encrypt(plaintext, "utf-8")
If jwe.LastMethodSuccess <> True Then
    Log(jwe.LastErrorText)
    Return
End If


'  Show the JWE we just created:
Log(strJwe)

'  Decrypt the JWE.
Dim jwe2 As ChilkatJwe
jwe2.Initialize
success = jwe2.LoadJwe(strJwe)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If

jwe2.SetWrappingKey(0, "000102030405060708090A0B0C0D0E0F", "hex")

'  Decrypt.
Dim originalPlaintext As String = jwe2.Decrypt(0, "utf-8")
If jwe2.LastMethodSuccess <> True Then
    Log(jwe2.LastErrorText)
    Return
End If


Log("original text: ")
Log(originalPlaintext)

'  Sample output:
'  eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
'  original text: 
'  Live long and prosper.