(Ruby) RSA Encrypt and Decrypt Credit Card Numbers

Ruby 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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require 'chilkat'

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

rsa = Chilkat::CkRsa.new()

key = Chilkat::CkPrivateKey.new()

# Load an RSA private key from a file:
success = key.LoadAnyFormatFile("rsaPrivateKey.key","")
if (success != true)
    print key.lastErrorText() + "\n";
    exit
end

# Get the key as XML:

keyXml = key.getXml()

# 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.
success = rsa.ImportPublicKey(keyXml)
if (success != true)
    print rsa.lastErrorText() + "\n";
    exit
end

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

usePrivateKey = false
rsa.put_EncodingMode("base64")
encryptedStr = rsa.encryptStringENC(ccNumber,usePrivateKey)
print "Encrypted:" + "\n";
print encryptedStr + "\n";

# Now decrypt:
rsaDecryptor = Chilkat::CkRsa.new()

rsaDecryptor.put_EncodingMode("base64")
success = rsaDecryptor.ImportPrivateKey(keyXml)

usePrivateKey = true
decryptedStr = rsaDecryptor.decryptStringENC(encryptedStr,usePrivateKey)

print "Decrypted:" + "\n";
print decryptedStr + "\n";

# 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