Tcl

JWE with Binary Data

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

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

Tcl

load ./chilkat.dll

set success 0

# 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.

# Load a JPG file that will be the JWE payload.
set jpgBytes [new_CkBinData]

set success [CkBinData_LoadFile $jpgBytes "qa_data/jpg/starfish.jpg"]
# Make sure your app checks the success/failure of the call to LoadFile..
puts "Original JPG size = [CkBinData_get_NumBytes $jpgBytes]"

set jwe [new_CkJwe]

set jweProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jweProtHdr "alg" "A128KW"
CkJsonObject_AppendString $jweProtHdr "enc" "A128CBC-HS256"
CkJwe_SetProtectedHeader $jwe $jweProtHdr

set aesWrappingKey "GawgguFyGrWKav7AX4VKUg"
CkJwe_SetWrappingKey $jwe 0 $aesWrappingKey "base64url"

# Encrypt and return the JWE in sbJwe:
set sbJwe [new_CkStringBuilder]

set success [CkJwe_EncryptBd $jwe $jpgBytes $sbJwe]
if {$success != 1} then {
    puts [CkJwe_lastErrorText $jwe]
    delete_CkBinData $jpgBytes
    delete_CkJwe $jwe
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwe
    exit
}

# Show the JWE:
puts [CkStringBuilder_getAsString $sbJwe]
puts "size of JWE: [CkStringBuilder_get_Length $sbJwe]"

# ---------------------------------------------------------
# Decrypt to get the original JPG file..

set jwe2 [new_CkJwe]

set success [CkJwe_LoadJweSb $jwe2 $sbJwe]
if {$success != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkBinData $jpgBytes
    delete_CkJwe $jwe
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwe
    delete_CkJwe $jwe2
    exit
}

# Set the AES wrap key.
CkJwe_SetWrappingKey $jwe2 0 $aesWrappingKey "base64url"

# Decrypt.
set jpgOriginal [new_CkBinData]

set success [CkJwe_DecryptBd $jwe2 0 $jpgOriginal]
if {$success != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkBinData $jpgBytes
    delete_CkJwe $jwe
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwe
    delete_CkJwe $jwe2
    delete_CkBinData $jpgOriginal
    exit
}

puts "Decrypted JPG size = [CkBinData_get_NumBytes $jpgOriginal]"

# Save the decrypted JPG to a file.
set success [CkBinData_WriteFile $jpgOriginal "qa_output/jwe_decrypted_starfish.jpg"]

puts "success = $success"

# The output of this program, when tested, was:
# Original JPG size = 6229
# eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
# size of JWE: 8473
# Decrypted JPG size = 6229
# success = True

delete_CkBinData $jpgBytes
delete_CkJwe $jwe
delete_CkJsonObject $jweProtHdr
delete_CkStringBuilder $sbJwe
delete_CkJwe $jwe2
delete_CkBinData $jpgOriginal