(Excel) RSA Encrypt and Decrypt Strings

Excel sample code to RSA public-key encrypt and decrypt strings using public and private keys.

Download Excel Class Modules Chilkat Excel Class Modules

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

Dim rsa As Chilkat.Rsa
Set rsa = Chilkat.NewRsa

' This example also generates the public and private
' keys to be used in the RSA encryption.
' Normally, you would generate a key pair once,
' and distribute the public key to your partner.
' Anything encrypted with the public key can be
' decrypted with the private key.  The reverse is 
' also true: anything encrypted using the private
' key can be decrypted using the public key.

' Generate a 1024-bit key.  Chilkat RSA supports
' key sizes ranging from 512 bits to 4096 bits.

success = rsa.GenerateKey(1024)
If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Keys are exported in XML format:

publicKey = rsa.ExportPublicKey()

privateKey = rsa.ExportPrivateKey()


plainText = "Encrypting and decrypting should be easy!"

' Start with a new RSA object to demonstrate that all we
' need are the keys previously exported:
Dim rsaEncryptor As Chilkat.Rsa
Set rsaEncryptor = Chilkat.NewRsa

' Encrypted output is always binary.  In this case, we want
' to encode the encrypted bytes in a printable string.
' Our choices are "hex", "base64", "url", "quoted-printable".
rsaEncryptor.EncodingMode = "hex"

' We'll encrypt with the public key and decrypt with the private
' key.  It's also possible to do the reverse.
success = rsaEncryptor.ImportPublicKey(publicKey)


usePrivateKey = False

encryptedStr = rsaEncryptor.EncryptStringENC(plainText,usePrivateKey)
Debug.Print encryptedStr

' Now decrypt:
Dim rsaDecryptor As Chilkat.Rsa
Set rsaDecryptor = Chilkat.NewRsa

rsaDecryptor.EncodingMode = "hex"
success = rsaDecryptor.ImportPrivateKey(privateKey)

usePrivateKey = True

decryptedStr = rsaDecryptor.DecryptStringENC(encryptedStr,usePrivateKey)

Debug.Print decryptedStr