I have tried to use this tutorial wiki.newae.com/Tutorial_B8_Prof … ate_Attack in order to make my first template attack in the first round of an AES.

My first experiment doesn’t give me good results, I have a nice Point of interest, however I don’t find any correct bytes from my secret key. So I decide to modify the template attack in order to attack the last round:

This the code to calculate the intermediate value for the first round and its hamming weight:

[code]# Useful utilities

sbox=(

0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,

0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,

0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,

0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,

0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,

0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,

0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,

0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,

0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,

0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,

0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,

0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,

0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,

0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,

0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,

0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16)

hw = [bin(x).count(“1”) for x in range(256)]

def cov(x, y):

# Find the covariance between two 1D lists (x and y).

# Note that var(x) = cov(x, x)

return np.cov(x, y)[0][1]

# Start calculating template

# 1: load data

tempTraces = np.load(r’C:\chipwhisperer\software\temp_attack\rand_key_data\traces\2016.05.24-12.53.15_traces.npy’)

tempPText = np.load(r’C:\chipwhisperer\software\temp_attack\rand_key_data\traces\2016.05.24-12.53.15_textin.npy’)

tempKey = np.load(r’C:\chipwhisperer\software\temp_attack\rand_key_data\traces\2016.05.24-12.53.15_keylist.npy’)

# 2: Find HW(sbox) to go with each input

# Note - we’re only working with the first byte here

tempSbox = [sbox[tempPText[i][0] ^ tempKey[i][0]] for i in range(len(tempPText))]

tempHW = [hw[s] for s in tempSbox]

[/code]

But I don’t find how to modify my code in order to calculate the intermediate value of the last round. As I know that:

```
[code]
```

The intermediate value of the last round= SubBytes^(-1)[ShiftRows^(-1)[k10♁ciphertext]]

[/code]

If I suppose that is correct, Mus I just change this equation in my code???

`tempSbox = [sbox[Ciphertext[i][0] ^ key[i][0]] for i in range(len(Ciphertext))] `

I would be very grateful if you could help me please: How to calculate please the intermediate value of the last round in python?