B4X

JWE using A256GCMKW

See more JSON Web Encryption (JWE) Examples

This example demonstrates creating a JCE with AES GCM key wrap. B4X

Dim success As Boolean = False

'  This requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

Dim plaintext As String = "My text to enrypt"

Dim jwe As ChilkatJwe
jwe.Initialize

'  First build the JWE Protected Header: 

'          {
'              "alg": "A256GCMKW",
'              "kid": "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d",
'              "tag": "kfPduVQ3T3H6vnewt--ksw",
'              "iv": "KkYT0GX_2jHlfqN_",
'              "enc": "A128CBC-HS256"
'          }

Dim jweProtHdr As ChilkatJsonObject
jweProtHdr.Initialize
jweProtHdr.AppendString("alg", "A256GCMKW")
'  kid is optional
jweProtHdr.AppendString("kid", "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d")
'  tag is optional
jweProtHdr.AppendString("tag", "kfPduVQ3T3H6vnewt--ksw")
jweProtHdr.AppendString("enc", "A256GCM")
'  the iv should be 16 random chars.
Dim prng As ChilkatPrng
prng.Initialize
jweProtHdr.AppendString("iv", prng.RandomString(16, True, True, True))
jwe.SetProtectedHeader(jweProtHdr)

Log("JWE Protected Header: " & jweProtHdr.Emit)
Log("--")

'  Given that we have 256-bit AES, our key should be 32 bytes.
'  The ascii string here is 32 bytes, therefore the 2nd arg is "ascii" to use these
'  ascii chars directly as the key.
Dim aesWrappingKey As String = "2baf4f730f5e4542b428593ef9cceb0e"
jwe.SetWrappingKey(0, aesWrappingKey, "ascii")

'  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 that was just produced.
'  1) Load the JWE.
'  2) Set the AES wrapping key.
'  3) Decrypt.
Dim jwe2 As ChilkatJwe
jwe2.Initialize
success = jwe2.LoadJwe(strJwe)
If success <> True Then
    Log(jwe2.LastErrorText)
    Return
End If

'  Set the AES wrap key.  Important to use "ascii"
jwe2.SetWrappingKey(0, aesWrappingKey, "ascii")

'  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)