Decryption does not work

[lim-jeongmin]

include "AESLib.h"

AESLib aesLib;

String text = "i am happy";

char cleartext[256]; char ciphertext[512];

// AES Encryption Key byte key[] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C };

// General initialization vector (you must use your own IV's in production for full security!!!) byte my_iv[N_BLOCK] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

String encrypt(char msg, byte iv[]) {
int msgLen = strlen(msg); char encrypted[2 msgLen]; aesLib.encrypt64(msg, msgLen, encrypted, key, sizeof(key), iv);
return String(encrypted); }

String decrypt(char * msg, byte iv[]) { unsigned long ms = micros(); int msgLen = strlen(msg); char decrypted[msgLen]; // half may be enough aesLib.decrypt64(msg, msgLen, decrypted, key, sizeof(key), iv);
return String(decrypted); }

void setup() { Serial.begin(115200); aesLib.gen_iv(my_iv);

text.toCharArray(cleartext, 256); // Encrypt String encrypted = encrypt(cleartext, my_iv); Serial.print("Ciphertext: "); Serial.println(encrypted); sprintf(ciphertext, "%s", encrypted.c_str());

// Decrypt String decrypted = decrypt(ciphertext, my_iv);

if(decrypted.length()!=0){ Serial.print("Cleartext: "); Serial.println(decrypted);
} else Serial.print("Cleartext: "); }

void loop() {

}

I tried with a little variation, it is not decrypted

[chim3y]

@lim-jeongmin i also experienced the same problem. AESlib generated different ciphertext as opposed to the one (https://www.devglan.com/online-tools/aes-encryption-decryption) and hence it decrypts differently.

Please, can you kindly suggest how did you fix the problem?

[suculent]

See https://github.com/suculent/thinx-aes-lib/issues/18 what padding do you use?

2. 5. 2020 v 7:36, chim3y notifications@github.com:

@lim-jeongmin i also experienced the same problem. AESlib generated different ciphertext as opposed to the one (https://www.devglan.com/online-tools/aes-encryption-decryption) and hence it decrypts differently.

Please, can you kindly suggest how did you fix the problem?

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[ElMohamed]

The array my_iv was overwritten by encryption, so you can not use my_iv again for decryption. Try this for example:

include "AESLib.h"

AESLib aesLib;

String text = "i am happy";

char cleartext[256]; char ciphertext[512];

// AES Encryption Key byte key[] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C };

// General initialization vector (you must use your own IV's in production for full security!!!) byte my_iv[N_BLOCK] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

String encrypt(char msg, byte iv[]) { int msgLen = strlen(msg); char encrypted[2 msgLen]; aesLib.encrypt64(msg, msgLen, encrypted, key, sizeof(key), iv); return String(encrypted); }

String decrypt(char * msg, byte iv[]) { unsigned long ms = micros(); int msgLen = strlen(msg); char decrypted[msgLen]; // half may be enough aesLib.decrypt64(msg, msgLen, decrypted, key, sizeof(key), iv); return String(decrypted); }

void setup() { Serial.begin(115200); //aesLib.gen_iv(my_iv); byte my_iv1[N_BLOCK] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C }; text.toCharArray(cleartext, 256); // Encrypt String encrypted = encrypt(cleartext, my_iv1); Serial.print("Ciphertext: "); Serial.println(encrypted); sprintf(ciphertext, "%s", encrypted.c_str());

byte my_iv2[N_BLOCK] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C }; // Decrypt String decrypted = decrypt(ciphertext, my_iv2);

if(decrypted.length()!=0){ Serial.print("Cleartext: "); Serial.println(decrypted); } else Serial.print("Cleartext: "); }

void loop() {

}

[suculent]

Of course. The iv gets changed with each block so you need to save the INITIAL value to decode the chain of blocks.

That’s how block cipher works.

M.

2. 5. 2020 v 15:30, ElMohamed notifications@github.com:

The array my_iv was overwritten by encryption, so you can not use my_iv again for decryption. Try this for example:

include "AESLib.h"

AESLib aesLib;

String text = "i am happy";

char cleartext[256]; char ciphertext[512];

// AES Encryption Key byte key[] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C };

// General initialization vector (you must use your own IV's in production for full security!!!) byte my_iv[N_BLOCK] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

String encrypt(char msg, byte iv[]) { int msgLen = strlen(msg); char encrypted[2 msgLen]; aesLib.encrypt64(msg, msgLen, encrypted, key, sizeof(key), iv); return String(encrypted); }

String decrypt(char * msg, byte iv[]) { unsigned long ms = micros(); int msgLen = strlen(msg); char decrypted[msgLen]; // half may be enough aesLib.decrypt64(msg, msgLen, decrypted, key, sizeof(key), iv); return String(decrypted); }

void setup() { Serial.begin(115200); //aesLib.gen_iv(my_iv); byte my_iv1[N_BLOCK] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C }; text.toCharArray(cleartext, 256); // Encrypt String encrypted = encrypt(cleartext, my_iv1); Serial.print("Ciphertext: "); Serial.println(encrypted); sprintf(ciphertext, "%s", encrypted.c_str());

byte my_iv2[N_BLOCK] = { 0x15, 0x2B, 0x7E, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C }; // Decrypt String decrypted = decrypt(ciphertext, my_iv2);

if(decrypted.length()!=0){ Serial.print("Cleartext: "); Serial.println(decrypted); } else Serial.print("Cleartext: "); }

void loop() {

}

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[ElMohamed]

Yes, indeed.

[ElMohamed]

@chim3y. Do you use AesLib::decrypt64 function if so at the python side you need to do the following: encod64(plaintext) - > encrypt(encoded64plaintex) - > encode64(encryptedEncode64plaintext)

Or you need to use AesLib:encrypt().

[chim3y]

@ElMohamed @suculent thank you much for your time and suggestions...it finally worked.

[ElMohamed]

Goed no problem