(Tcl) Create a JWS Using ECDSA P-256 SHA-256

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

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

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load ./chilkat.dll

# 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.

# Use the following ECC key loaded from JWK format.
set sbJwk [new_CkStringBuilder]

CkStringBuilder_Append $sbJwk "{\"kty\":\"EC\","
CkStringBuilder_Append $sbJwk "\"crv\":\"P-256\","
CkStringBuilder_Append $sbJwk "\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\","
CkStringBuilder_Append $sbJwk "\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\","
CkStringBuilder_Append $sbJwk "\"d\":\"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI\""
CkStringBuilder_Append $sbJwk "}"

set eccKey [new_CkPrivateKey]

# Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
# into the private key object. (See the online reference documentation..)
set success [CkPrivateKey_LoadJwk $eccKey [CkStringBuilder_getAsString $sbJwk]]
if {$success != 1} then {
    puts [CkPrivateKey_lastErrorText $eccKey]
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $eccKey
    exit
}

# Create the JWS Protected Header
set jwsProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jwsProtHdr "alg" "ES256"

set jws [new_CkJws]

# Set the protected header:
set signatureIndex 0
CkJws_SetProtectedHeader $jws $signatureIndex $jwsProtHdr

# Set the ECC key:
CkJws_SetPrivateKey $jws $signatureIndex $eccKey

# Set the payload.
set bIncludeBom 0
set payloadStr "In our village, folks say God crumbles up the old moon into stars."
CkJws_SetPayload $jws $payloadStr "utf-8" $bIncludeBom

# Create the JWS
# By default, the compact serialization is used.
set jwsCompact [CkJws_createJws $jws]
if {[CkJws_get_LastMethodSuccess $jws] != 1} then {
    puts [CkJws_lastErrorText $jws]
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $eccKey
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    exit
}

puts "JWS: $jwsCompact"

# Note: ECC signatures use random values, so the output will be different each time a signature is produced.
# sample output:
# JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

# Now load the JWS, validate, and recover the original text.
set jws2 [new_CkJws]

# Load the JWS.
set success [CkJws_LoadJws $jws2 $jwsCompact]

# eccPubKey is a CkPublicKey
set eccPubKey [CkPrivateKey_GetPublicKey $eccKey]

# Set the ECC public key used for validation.
set signatureIndex 0
CkJws_SetPublicKey $jws2 $signatureIndex $eccPubKey
delete_CkPublicKey $eccPubKey

# Validate the 1st (and only) signature at index 0..
set v [CkJws_Validate $jws2 $signatureIndex]
if {$v < 0} then {
    # Perhaps Chilkat was not unlocked or the trial expired..
    puts "Method call failed for some other reason."
    puts [CkJws_lastErrorText $jws2]
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $eccKey
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

if {$v == 0} then {
    puts "Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both."
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $eccKey
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

# If we get here, the signature was validated..
puts "Signature validated."

# Recover the original content:
puts [CkJws_getPayload $jws2 utf-8]

# Examine the protected header:
# joseHeader is a CkJsonObject
set joseHeader [CkJws_GetProtectedHeader $jws2 $signatureIndex]
if {[CkJws_get_LastMethodSuccess $jws2] != 1} then {
    puts "No protected header found at the given index."
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $eccKey
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

puts "Protected (JOSE) header:"
puts [CkJsonObject_emit $joseHeader]
delete_CkJsonObject $joseHeader

# Output:

# Signature validated.
# In our village, folks say God crumbles up the old moon into stars.
# Protected (JOSE) header:
# { 
#   "alg": "ES256"
# }

delete_CkStringBuilder $sbJwk
delete_CkPrivateKey $eccKey
delete_CkJsonObject $jwsProtHdr
delete_CkJws $jws
delete_CkJws $jws2