func EncryptAES_CBC_Manual(plainText, key string) []byte {
keyBytes := secutils.ASCIIStringToBytes(key)
plainTextBytes := secutils.ASCIIStringToBytes(plainText)
blocks := len(plainTextBytes) / BlockSize
mod := len(plainTextBytes) % BlockSize
if mod != 0 {
blocks++
}
iv := make([]byte, BlockSize)
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
panic(err)
}
var buffer bytes.Buffer
previousBlock := iv
buffer.Write(iv)
for block := 0; block < blocks; block++ {
// this is the last block which may need padding
if block == blocks-1 {
start := block * BlockSize
data := plainTextBytes[start:]
// just make sure it is padded
// the Pkcs7 function takes care of double check it
originalData := Pkcs7(data, BlockSize)
// XOR with the previous block
xored := secutils.XorBytes(originalData, previousBlock)
cipherBlock := Encrypt_Block(xored, keyBytes)
buffer.Write(cipherBlock)
} else {
start := block * BlockSize
end := start + BlockSize
// XOR with the previous block
originalData := plainTextBytes[start:end]
xored := secutils.XorBytes(originalData, previousBlock)
// Encrypt with the XORED data and assign the result to the previous block for the next cycle !
cipherBlock := Encrypt_Block(xored, keyBytes)
// #### THIS IS REALLY IMPORTANT !!!!!
// otherwise it is completely broken !!!!
previousBlock = cipherBlock
buffer.Write(cipherBlock)
}
}
return buffer.Bytes()
}
func DecryptAES_CBC_Manual(cipherTextBytes, keyBytes []byte) []byte {
blocks := (len(cipherTextBytes) / BlockSize) - 1 // we have to remove the IV
//mod := len(cipherTextBytes) % BlockSize
//if mod != 0 {
// panic("ciphertext is not a multiple of the block size ")
//}
iv := cipherTextBytes[:BlockSize]
remainingBytes := cipherTextBytes[BlockSize:]
previousBlock := iv
var buffer bytes.Buffer
for block := 0; block < blocks; block++ {
blockBytes := remainingBytes[:BlockSize]
remainingBytes = remainingBytes[BlockSize:]
decryptedBlock := Decrypt_Block(blockBytes, keyBytes)
xored := secutils.XorBytes(previousBlock, decryptedBlock)
buffer.Write(xored)
previousBlock = blockBytes
}
decryptedBytes := buffer.Bytes()
if IsPkcs7(decryptedBytes, BlockSize) {
decryptedBytes = Unpad_Pkcs7(decryptedBytes, BlockSize)
}
return decryptedBytes
}
