AES
Advanced Encryption Standard，縮寫：AES，又稱Rijndael加密法，但嚴格來說 AES 和 Rijndael 加密法並不完全一樣，因為 Rijndael 加密法可以支援更大範圍的區塊長度，AES的區塊長度固定為128位元而Rijndael使用的區塊長度可以是128，192或256位元。AES用來替代原先的DES。
AES的區塊長度固定為 128 位元，金鑰長度則可以是128，192或256位元；而Rijndael使用的金鑰和區塊長度均可以是128，192或256位元。
AES加密過程是在一個4×4的位元組矩陣上運作，其初值即為一個明文區塊，矩陣中一個元素大小就是明文區塊中的一個Byte。
其加密方法主要包含四個步驟
Copy 1. AddRoundKey: 將每個狀態中的位元組與該回合金鑰做異或（⊕）。
2. SubBytes: 矩陣中各位元組被固定的8位元尋找表中對應的特定位元組所替換。
3. ShiftRows: 矩陣中每一行的各個位元組循環向左方位移。位移量則隨著行數遞增而遞增。
4. MixColumns: 每個直行與 AES 定義的多項式 c(x) 進行多項式乘法。 AES-256 範例
Copy const crypto = require ( 'crypto' );
const mode = 'aes256' // 可更換為aes128或aes192等等
// 加密
const cipher = crypto .createCipher (mode , 'a password' );
let encrypted = cipher .update ( 'I_am_plaintext' , 'utf8' , 'hex' );
encrypted += cipher .final ( 'hex' );
console .log (encrypted);
// 解密
const decipher = crypto .createDecipher (mode , 'a password' );
let decrypted = decipher .update (encrypted , 'hex' , 'utf8' );
decrypted += decipher .final ( 'utf8' );
console .log (decrypted); AES之區塊加密模式
在CBC、OFB、CFB、CTR等區塊模式 IV 長度均為 16 bytes，GCM模式的 IV 則沒有一定要 16 bytes
AES-256-CBC範例
Copy const crypto = require ( 'crypto' );
// 因為aes-256要求之key 長度為256bits 也就是32 bytes = 32個ASCII英文字母
// aes-128 要求之key 長度為128bits 也就是16 bytes = 16個英文字母
let key = Buffer .from ( "abcbbbbbbbbbbbbbabcbbbbbbbbbbbbb" , 'utf-8' ) //or crypto.randomBytes(32);
const IV_LENGTH = 16 ;
function encrypt (text) {
let iv = crypto .randomBytes ( IV_LENGTH );
// 可直接替換為ofb、cfb、ctr等模式
let cipher = crypto .createCipheriv ( 'aes-256-cbc' , new Buffer (key) , iv);
let encrypted = cipher .update (text);
encrypted = cipher .final ();
// 將IV附上 在解密時須告知
return iv .toString ( 'hex' ) + ':' + encrypted .toString ( 'hex' );
}
function decrypt (text) {
let textParts = text .split ( ':' );
let iv = new Buffer ( textParts .shift () , 'hex' );
let encryptedText = new Buffer ( textParts .join ( ':' ) , 'hex' );
let decipher = crypto .createDecipheriv ( 'aes-256-cbc' , new Buffer (key) , iv);
let decrypted = decipher .update (encryptedText);
decrypted = decipher .final ();
return decrypted .toString ();
}
console .log ( encrypt ( "test" ));
console .log ( decrypt ( encrypt ( "test" ))) AES-256-GCM範例
需要加上cipher.getAuthTag(); 與 decipher.setAuthTag();
目前 AuthTag 與 Additional Authenticated Data ( AAD ) 在 Node.js 只有 GCM 模式支援，cipher.setAAD需要在 update() 之前使用，而 cipher.getAuthTag() 必須要在cipher.final()
Copy const crypto = require ( 'crypto' );
const mode = 'aes-256-gcm' ;
// 因為aes-256要求之key 長度為256bits 也就是32 bytes = 32個ASCII英文字母
// aes-128 要求之key 長度為128bits 也就是16 bytes = 16個英文字母
let key = Buffer .from ( "abcbbbbbbbbbbbbbabcbbbbbbbbbbbbb" , 'utf-8' ) //or crypto.randomBytes(32);
const IV_LENGTH = 12 ;
let tag;
function encrypt (text) {
let iv = crypto .randomBytes ( IV_LENGTH );
let cipher = crypto .createCipheriv (mode , new Buffer (key) , iv);
let encrypted = cipher .update (text , 'utf8' , 'hex' );
encrypted += cipher .final ( 'hex' );
// 需要加上AuthTag
tag = cipher .getAuthTag ();
// 將IV附上 在解密時須告知
return iv .toString ( 'hex' ) + ':' + encrypted .toString ( 'hex' );
}
function decrypt (text) {
let textParts = text .split ( ':' );
let iv = new Buffer ( textParts .shift () , 'hex' );
let encryptedText = new Buffer ( textParts .join ( ':' ) , 'hex' );
let decipher = crypto .createDecipheriv (mode , new Buffer (key) , iv);
// 需要加上AuthTag
decipher .setAuthTag (tag);
let decrypted = decipher .update (encryptedText , 'hex' , 'utf8' );
decrypted += decipher .final ( 'utf8' );
return decrypted .toString ();
}
console .log ( encrypt ( "test" ));
console .log ( decrypt ( encrypt ( "test" ))) IV 與 AuthTag
Copy IV and the auth tag can be sent in plain.
The auth tag is a tag the recipient can use to verify that the message has not been altered. This is important because AES-GCM acts as a stream cipher and anyone could flip bits.
The IV is not a secret, the only thing to be concerned about is that it must not be reused with the same key. 使用openssl加密檔案
Copy 產生檔案
echo test > file.txt
加密
openssl enc -aes-256-cbc -salt -in file.txt -out file.txt.enc
解密
openssl enc -aes-256-cbc -d -in file.txt.enc -out result.txt 加上密碼
Copy openssl enc -aes-256-cbc -salt -in file.txt -out file.txt.enc -k PASS
openssl enc -aes-256-cbc -d -in file.txt.enc -out file.txt -k PASS https://www.shellhacks.com/encrypt-decrypt-file-password-openssl/
