(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.)

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load ./chilkat.dll

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

set rsa [new_CkRsa]

set key [new_CkPrivateKey]

# Load an RSA private key from a file:
set success [CkPrivateKey_LoadAnyFormatFile $key "rsaPrivateKey.key" ""]
if {$success != 1} then {
    puts [CkPrivateKey_lastErrorText $key]
    delete_CkRsa $rsa
    delete_CkPrivateKey $key
    exit
}

# Get the key as XML:

set keyXml [CkPrivateKey_getXml $key]

# We'll encrypt with the public key and decrypt with the private
# key.  (It's also possible to do the reverse.)
# Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
# An RSA public-key is a sub-set of the private key.
# Therefore, when you have a private key, you really have
# both public and private keys.
set success [CkRsa_ImportPublicKey $rsa $keyXml]
if {$success != 1} then {
    puts [CkRsa_lastErrorText $rsa]
    delete_CkRsa $rsa
    delete_CkPrivateKey $key
    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"
set success [CkRsa_ImportPrivateKey $rsaDecryptor $keyXml]

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 $key
delete_CkRsa $rsaDecryptor