请以伪代码形式描述SPN线性密码分析算法的流程

Sure, here's a simplified pseudocode description of the Simplified Power Analysis (SPA) algorithm for linear cryptanalysis, which is commonly used to attack block ciphers with weak key dependencies:

// Initialize variables
plaintexts = [] // Array of input plaintexts for chosen plaintext attacks
sBoxOutputs = [] // Output from cipher after applying S-boxes
keyGuesses = [] // Candidate keys being tested

// Step 1: Choose plaintexts (often power traces)
for i from 0 to number_of_traces:
    plaintexts.append(power_trace(i)) // e.g., XORing with known patterns

// Step 2: Encrypt chosen plaintexts
for each plaintext in plaintexts:
    cipherText = encrypt(plaintext, current_key_guess)
    sBoxOutputs.append(cipherText_after_sbox)

// Step 3: Perform statistical analysis
meanDifference = calculate_mean_difference(sBoxOutputs) // Check average difference between output pairs

// Step 4: Update key guess based on results
if meanDifference is significant:
    update_key_guess(meanDifference) // Improve or refine the guessed key

// Repeat steps 2-4 for multiple rounds or until convergence