VigenereCipher.Psm1
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Function Lock-Vigenere ($PlainText, $key)
{ <# .SYNOPSIS 'Encrypts' data using Vigenere Cipher .DESCRIPTION Simple Vigenere cipher (https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher) encryption. .PARAMETER Plaintext The plaintext to encrypt. All spaces are elimated and then the plaintext is converted to uppercase .PARAMETER Key The key to encrypt the plaintext .Example New-Vigenere -PlainText "This is a test" -Key "abc" .INPUTS No inputs required .OUTPUTS Returns ciphertext .NOTES Author: Tim Jardim Date: 21.03.18 Version:1.001.002 #> ###################################################################### # Create our arrays to hold bytes for Ciphertext and Key [Byte[]]$PlainTextBytes=@();[Byte[]]$CipherTextBytes=@();[Byte[]]$KeyBytes=@() # Get data # Remove any spaces in PlainText $PlainText=$PlainText.Replace(" ","") # Convert PlainText to upper $PlainText=$PlainText.ToUpper() # Remove any spaces from key $Key=$Key.Replace(" ","") # Convert key to upper $Key=$Key.ToUpper() # Convert PlainText to bytes $ConvertToASCII = [System.Text.Encoding]::ASCII $ConvertToBytes = [system.Text.Encoding]::UTF8 $PlainTextBytes = $ConvertToBytes.GetBytes($Plaintext) $KeyBytes = $ConvertToBytes.GetBytes($Key) $KeyCount=0 # Cycle through plaintext to convert to ciphertext For ($I=0;$I -lt ($PlainTextBytes.Count);$I++) { # Strip out non alphabetic charcters allow only ASCII 65-90 (A-Z) If ($PlainTextBytes[$I] -gt 65 -or $PlainTextBytes -lt 90) { # Take byte value of plaintext and add with byte value of key. Last step is to take result and mod 26. The number 65 is used to offset ASCII value. A is ASCII value 65 $CipherTextBytes += ((($PlainTextBytes[$I] -65) + ($KeyBytes[$KeyCount] -65)) % 26) + 65 # Get next character in key $KeyCount ++ # Check whether or not key needs to be reset If ($KeyCount -gt ($Key.Length)-1) {$KeyCount=0} } } # Convert CiperTextBytes to ASCII $CipherText=$ConvertToASCII.GetString($CipherTextBytes) # Display reults Return $CipherText } Function Unlock-Vigenere ($Ciphertext,$Key) { <# .SYNOPSIS 'Decrypts' data using Vigenere Cipher .DESCRIPTION Simple Vigenere cipher (https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher) encryption. .PARAMETER Ciphertext The ciphertext to decrypt. All spaces are elimated and then the ciphertext is converted to uppercase .PARAMETER Key The key to decrypt the plaintext .Example New-Vigenere -CipherText "tiksjubvvaugsu" -Key "abc" .INPUTS No inputs required .OUTPUTS returns Plaintext .NOTES Author: Tim Jardim Date: 21.03.18 Version:1.001.002 #> ###################################################################### # Check to make sure that Ciphertext and key length is not 0 If (($CipherText.Length) -eq 0 -or ($Key.Length) -eq 0) { Return $false } # Create our arrays to hold bytes for Ciphertext and Key [Byte[]]$PlainTextBytes=@();[Byte[]]$CipherTextBytes=@();[Byte[]]$KeyBytes=@() # Remove any spaces from ciphertext $CipherText=$CipherText.Replace(" ","") # Convert ciphertext to upper $CipherText=$CipherText.ToUpper() # Remove any spaces from key $Key=$Key.Replace(" ","") # Convert key to upper $Key=$Key.ToUpper() # Convert PlainText to bytes $ConvertToASCII = [System.Text.Encoding]::ASCII $ConvertToBytes = [system.Text.Encoding]::UTF8 $CipherTextBytes = $ConvertToBytes.GetBytes($Ciphertext) $KeyBytes = $ConvertToBytes.GetBytes($Key) $KeyCount=0 # Cycle through plaintext to convert to ciphertext For ($I=0;$I -lt ($CipherTextBytes.Count);$I++) { # Strip out non alphabetic charcters allow only ASCII 65-90 (A-Z) If ($CipherTextBytes[$I] -gt 65 -or $CipherTextBytes -lt 90) { # Pause # Take byte value of plaintext and add with byte value of key. Last step is to take result (add 26 incase result is less than 65) and mod 26. The number 65 is used to offset ASCII value. A is ASCII value 65 $PlainTextBytes += (((($CipherTextBytes[$I] -65) - ($KeyBytes[$KeyCount] -65))+26) % 26) + 65 # Get next character in key $KeyCount ++ # Check whether or not key needs to be reset If ($KeyCount -gt ($Key.Length)-1) {$KeyCount=0} } } # Convert CiperTextBytes to ASCII $PlainText=$ConvertToASCII.GetString($PlainTextBytes) # Display reults Return $PlainText } |