python中有没有任何方法可以用key进行SHA1散列？

Question

我需要使用SHA-1作为PRNG，所以这就是为什么它需要一些密钥，但是在python libs中，比如hashlib和pycryptodome，我没有找到任何这样的机会。有现成的解决办法吗？或者在python中有另一种使用SHA-1作为PRNG的方法？问这个问题是因为NIST测试中的SHA-1 PRNG代码让我有点困惑（代码来自NIST测试，最后在sts-2.1.2/sts-2.1.2/src/generators.c中）。老实说，我原以为SHA-1 PRNG是这样工作的：

1. 我们有一些起始值（设为x），然后我们做一些类似于r=sha1(x)
2. 现在我们把r作为伪随机序列的一个新成员
3. 为了有另一个成员，我们做r=sha1(r) 但是有了NIST的代码，我真的不明白如何在python上实现SHA-1prng

//  Uses 160 bit Xkey and no XSeed (b=160)
//  This is the generic form of the generator found on the last page of the Change Notice for FIPS 186-2
void
SHA1()
{
    ULONG   A, B, C, D, E, temp, Wbuff[16];
    BYTE    Xkey[20], G[20], M[64];
    BYTE    One[1] = { 0x01 };
    int     i, num_0s, num_1s, bitsRead;
    int     done;
    ULONG   tx[5] = { 0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0 };

    if ( ((epsilon = (BitSequence *) calloc(tp.n,sizeof(BitSequence))) == NULL) ) {
        printf("Insufficient memory available.\n");
        exit(1);
    }

    ahtopb("ec822a619d6ed5d9492218a7a4c5b15d57c61601", Xkey, 20);
//  ahtopb("E65097BAEC92E70478CAF4ED0ED94E1C94B15446", Xkey, 20);
//  ahtopb("6BFB9EC9BE37B2B0FF8526C222B76E0E91501753", Xkey, 20);
//  ahtopb("5AE8B9207250257D0A0C87C0DACEF78E17D1EF9D", Xkey, 20);
//  ahtopb("D99CB53DD5FA9BC1D0176F5DF8D9110FD16EE21F", Xkey, 20);

    for ( i=0; i<tp.numOfBitStreams; i++ ) {
        num_0s = 0;
        num_1s = 0;
        bitsRead = 0;
        do {
            memcpy(M, Xkey, 20);
            memset(M+20, 0x00, 44);

            // Start: SHA Steps A-E
            A = tx[0];
            B = tx[1];
            C = tx[2];
            D = tx[3];
            E = tx[4];

            memcpy((BYTE *)Wbuff, M, 64);
#ifdef LITTLE_ENDIAN
            byteReverse(Wbuff, 20);
#endif
            sub1Round1( 0 );  sub1Round1( 1 );  sub1Round1( 2 );  sub1Round1( 3 );
            sub1Round1( 4 );  sub1Round1( 5 );  sub1Round1( 6 );  sub1Round1( 7 );
            sub1Round1( 8 );  sub1Round1( 9 );  sub1Round1( 10 ); sub1Round1( 11 );
            sub1Round1( 12 ); sub1Round1( 13 ); sub1Round1( 14 ); sub1Round1( 15 );
            sub2Round1( 16 ); sub2Round1( 17 ); sub2Round1( 18 ); sub2Round1( 19 );
            Round2( 20 ); Round2( 21 ); Round2( 22 ); Round2( 23 );
            Round2( 24 ); Round2( 25 ); Round2( 26 ); Round2( 27 );
            Round2( 28 ); Round2( 29 ); Round2( 30 ); Round2( 31 );
            Round2( 32 ); Round2( 33 ); Round2( 34 ); Round2( 35 );
            Round2( 36 ); Round2( 37 ); Round2( 38 ); Round2( 39 );
            Round3( 40 ); Round3( 41 ); Round3( 42 ); Round3( 43 );
            Round3( 44 ); Round3( 45 ); Round3( 46 ); Round3( 47 );
            Round3( 48 ); Round3( 49 ); Round3( 50 ); Round3( 51 );
            Round3( 52 ); Round3( 53 ); Round3( 54 ); Round3( 55 );
            Round3( 56 ); Round3( 57 ); Round3( 58 ); Round3( 59 );
            Round4( 60 ); Round4( 61 ); Round4( 62 ); Round4( 63 );
            Round4( 64 ); Round4( 65 ); Round4( 66 ); Round4( 67 );
            Round4( 68 ); Round4( 69 ); Round4( 70 ); Round4( 71 );
            Round4( 72 ); Round4( 73 ); Round4( 74 ); Round4( 75 );
            Round4( 76 ); Round4( 77 ); Round4( 78 ); Round4( 79 );

            A += tx[0];
            B += tx[1];
            C += tx[2];
            D += tx[3];
            E += tx[4];

            memcpy(G, (BYTE *)&A, 4);
            memcpy(G+4, (BYTE *)&B, 4);
            memcpy(G+8, (BYTE *)&C, 4);
            memcpy(G+12, (BYTE *)&D, 4);
            memcpy(G+16, (BYTE *)&E, 4);
#ifdef LITTLE_ENDIAN
            byteReverse((ULONG *)G, 20);
#endif
            // End: SHA Steps A-E

            done = convertToBits(G, 160, tp.n, &num_0s, &num_1s, &bitsRead);
            add(Xkey, 20, G, 20);
            add(Xkey, 20, One, 1);
        } while ( !done );
        fprintf(freqfp, "\t\tBITSREAD = %d 0s = %d 1s = %d\n", bitsRead, num_0s, num_1s); fflush(freqfp);
        nist_test_suite();
    }
    free(epsilon);
}