(Tcl) RSA Encrypt and Decrypt Credit Card Numbers

Tcl sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

Note: This example requires Chilkat v11.0.0 or greater.

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load ./chilkat.dll

set success 0

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

set rsa [new_CkRsa]

set privKey [new_CkPrivateKey]

# Load an RSA private key from a file:
set success [CkPrivateKey_LoadAnyFormatFile $privKey "rsaPrivateKey.key" ""]
if {$success == 0} then {
    puts [CkPrivateKey_lastErrorText $privKey]
    delete_CkRsa $rsa
    delete_CkPrivateKey $privKey
    exit
}

# Get the public part of the private key.
set pubKey [new_CkPublicKey]

CkPrivateKey_ToPublicKey $privKey $pubKey

set success [CkRsa_UsePublicKey $rsa $pubKey]
if {$success == 0} then {
    puts [CkRsa_lastErrorText $rsa]
    delete_CkRsa $rsa
    delete_CkPrivateKey $privKey
    delete_CkPublicKey $pubKey
    exit
}

# Encrypt a VISA credit card number:
# 1234-5678-0000-9999
set ccNumber "1234567800009999"

set usePrivateKey 0
CkRsa_put_EncodingMode $rsa "base64"
set encryptedStr [CkRsa_encryptStringENC $rsa $ccNumber $usePrivateKey]
puts "Encrypted:"
puts "$encryptedStr"

# Now decrypt:
set rsaDecryptor [new_CkRsa]

CkRsa_put_EncodingMode $rsaDecryptor "base64"
CkRsa_UsePrivateKey $rsaDecryptor $privKey

set usePrivateKey 1
set decryptedStr [CkRsa_decryptStringENC $rsaDecryptor $encryptedStr $usePrivateKey]

puts "Decrypted:"
puts "$decryptedStr"

# Important: RSA encryption should only be used to encrypt small amounts of data.
# It is typically used for encrypting symmetric encryption
# keys such that a symmetric encryption algorithm, such as 
# AES is then used to encrypt/decrypt bulk data

delete_CkRsa $rsa
delete_CkPrivateKey $privKey
delete_CkPublicKey $pubKey
delete_CkRsa $rsaDecryptor