cyrildever / feistel Goto Github PK

Wikipedia's definition of FPE as:

In cryptography, format-preserving encryption (FPE), refers to encrypting in such a way that the output (the ciphertext) is in the same format as the input (the plaintext). The meaning of "format" varies. Typically only finite sets of characters are used; numeric, alphabetic or alphanumeric. For example:

• Encrypting a 16-digit credit card number so that the ciphertext is another 16-digit number.
• Encrypting an English word so that the ciphertext is another English word.
• Encrypting an n-bit number so that the ciphertext is another n-bit number (this is the definition of an n-bit block cipher).

However, the result obtained by encrypting the original data with Encrypt() does not seem to be in the same format as the original data.
For example, the encrypted number 123123123123, according to FPE, what I get should be a string of pure numbers, but what I actually get is `ZW±ªX^²[[®R.
Did we just keep the same length?

My Test Code

	source := "my-source-data"
	cipher := feistel.NewFPECipher(hash.SHA_256, "some-32-byte-long-key-to-be-safe", 128)

	obfuscated, err := cipher.Encrypt(source)
	assert.NoError(t, err)
	str := obfuscated.String()
	fmt.Println(str)
	assert.Equal(t, len(source), len(str))

My Result

        	Error:      	Not equal: 
        	            	expected: 21
        	            	actual  : 14
        	Test:       	TestFormatPreservingEncryption

My OS

MacOS 12.6 M1

Version

github.com/cyrildever/feistel v1.3.21