feat: aes ctr

main.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"fmt"
+	"math"
+	"encoding/binary"
 	"encoding/hex"
 	"crypto/aes"
 	"github.com/spf13/afero"
@@ -32,4 +34,91 @@ func main() {
 	fmt.Println(hex.EncodeToString(key))
 	fmt.Println(hex.EncodeToString(src))
 	fmt.Println(hex.EncodeToString(dest))
+
+
+	fmt.Println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>")
+	nonce, err := hex.DecodeString("0011223344556677ffffffffffffffff")
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println(hex.EncodeToString(nonce))
+	newNonce := nonceAdd(nonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+	newNonce = nonceAdd(newNonce, 1)
+	fmt.Println(hex.EncodeToString(newNonce))
+
+
+	fmt.Println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>")
+	test_key := []byte {
+		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+	}
+	test_iv := []byte {
+		1, 2, 3, 4, 5, 6, 7, 8, 0, 0, 0, 0, 0, 0, 0, 0,
+	}
+	plaintext := "hello world.hello world.hello world.hello world.hello world.hello world."
+	plaintextBytes := []byte(plaintext)
+
+	e, err := generateCtrEncryptBytes(test_key, test_iv, 0, int64(len(plaintextBytes)))
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println(hex.EncodeToString(e))
+	for i := 0; i < len(plaintextBytes); i++ {
+		plaintextBytes[i] = plaintextBytes[i] ^ e[i]
+	}
+	// SHOULD BE: 84ad8d80732490c061177a58bd26d032d6fcff2e66f9afe3cf95717485d3a4485d4a2a7bd835df3d0756b8192e3bf5a287ad8dd81942c43bc812c82d666ebbb34df4e2a5069467d9
+	fmt.Println(hex.EncodeToString(plaintextBytes))
+}
+
+func generateCtrEncryptBytes(key, iv []byte, offset, len int64) ([]byte, error) {
+	endOffset := offset + len
+	encryptStartOffset := (offset / 16) * 16
+	encryptEndOffset := (endOffset / 16) * 16
+	if endOffset % 16 > 0 {
+		encryptEndOffset += 16
+	}
+	blocksCount := int((encryptEndOffset - encryptStartOffset) / 16)
+
+	cipher, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	encryptBytes := make([]byte, blocksCount * 16)
+	for i := 0; i < blocksCount; i++ {
+		encNonce := nonceAdd(iv, uint64(i))
+		cipher.Encrypt(encryptBytes[i*16:(i+1)*16], encNonce)
+	}
+	// fmt.Println("XX ", hex.EncodeToString(encryptBytes))
+	return encryptBytes[offset-encryptStartOffset:offset-encryptStartOffset+len], nil
+}
+
+func nonceAdd(nonce []byte, incrementValue uint64) []byte {
+	n1 := binary.BigEndian.Uint64(nonce[:8])
+	n2 := binary.BigEndian.Uint64(nonce[8:])
+
+	leftToMax := math.MaxUint64 - n2
+	if leftToMax <= incrementValue {
+		incrementValue -= leftToMax + 1
+		n2 = incrementValue
+		n1 += 1
+	} else {
+		n2 += incrementValue
+	}
+
+	newNonce := make([]byte, 16)
+	binary.BigEndian.PutUint64(newNonce, n1)
+	binary.BigEndian.PutUint64(newNonce[8:], n2)
+	return newNonce
 }