BLISS.py 文件源码

def Sign(**kwargs):
    '''
    Algorithm 1, Pg 12 of BLISS paper
    o/p:
    z,c 
    '''
    msg, A, S, m, n, sd, q, M, kappa = kwargs['msg'], kwargs['A'], kwargs['S'], kwargs['m'], kwargs['n'], kwargs['sd'], kwargs['q'], kwargs['M'], kwargs['kappa']
    m_bar = m + n
    D = DiscreteGaussianDistributionLatticeSampler(ZZ**m_bar, sd)
    count = 0
    while(True):
        y = np.array(D()) # m' x 1 
        reduced_Ay = util.vector_to_Zq(np.matmul(A, y), 2*q)
        c = hash_iterative(np.array_str(reduced_Ay) + msg, n, kappa) # still not the hash but this is test run      
        b = util.crypt_secure_randint(0, 1)
        Sc = np.matmul(S,c)
        z = y + ((-1)**b) * Sc
        try:            
            exp_term = exp(float(Sc.dot(Sc)) / (2*sd**2))
            cosh_term = np.cosh(float(z.dot(Sc)) / (sd**2))
            val = exp_term / (cosh_term * M)                
        except OverflowError:
            print "OF"          
            continue            
        if(random.random() < min(val, 1.0)):
            break
        if(count > 10): # beyond 4 rejection sampling iterations are not expected in general 
            raise ValueError("The number of rejection sampling iterations are more than expected")
        count += 1                              
    return z, c