Dataset_Construction/projects/incubator-milagro-crypto/rust/src/mpin.rs

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regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
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  http://www.apache.org/licenses/LICENSE-2.0

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software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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specific language governing permissions and limitations
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use std::time::SystemTime;
use std::time::UNIX_EPOCH;

use super::big;
use super::big::Big;
use super::ecp;
use super::ecp::ECP;
use super::ecp2::ECP2;
use super::fp12::FP12;
use super::fp4::FP4;
use super::pair;
use super::rom;
use crate::hash256::HASH256;
use crate::hash384::HASH384;
use crate::hash512::HASH512;
use crate::rand::RAND;

// MPIN API Functions

// Configure mode of operation
pub const EFS: usize = big::MODBYTES as usize;
pub const EGS: usize = big::MODBYTES as usize;
pub const BAD_PARAMS: isize = -11;
pub const INVALID_POINT: isize = -14;
pub const WRONG_ORDER: isize = -18;
pub const BAD_PIN: isize = -19;
pub const SHA256: usize = 32;
pub const SHA384: usize = 48;
pub const SHA512: usize = 64;

// Configure your PIN here
pub const MAXPIN: i32 = 10000; // PIN less than this
pub const PBLEN: i32 = 14; // Number of bits in PIN
pub const TS: usize = 10; // 10 for 4 digit PIN, 14 for 6-digit PIN - 2^TS/TS approx = sqrt(MAXPIN)
pub const TRAP: usize = 200; // 200 for 4 digit PIN, 2000 for 6-digit PIN  - approx 2*sqrt(MAXPIN)

#[allow(non_snake_case)]
fn hash(sha: usize, c: &mut FP4, U: &mut ECP, r: &mut [u8]) -> bool {
    let mut w: [u8; EFS] = [0; EFS];
    let mut t: [u8; 6 * EFS] = [0; 6 * EFS];

    c.geta().geta().to_bytes(&mut w);
    for i in 0..EFS {
        t[i] = w[i]
    }
    c.geta().getb().to_bytes(&mut w);
    for i in EFS..2 * EFS {
        t[i] = w[i - EFS]
    }
    c.getb().geta().to_bytes(&mut w);
    for i in 2 * EFS..3 * EFS {
        t[i] = w[i - 2 * EFS]
    }
    c.getb().getb().to_bytes(&mut w);
    for i in 3 * EFS..4 * EFS {
        t[i] = w[i - 3 * EFS]
    }

    U.getx().to_bytes(&mut w);
    for i in 4 * EFS..5 * EFS {
        t[i] = w[i - 4 * EFS]
    }
    U.gety().to_bytes(&mut w);
    for i in 5 * EFS..6 * EFS {
        t[i] = w[i - 5 * EFS]
    }

    if sha == SHA256 {
        let mut h = HASH256::new();
        h.process_array(&t);
        let sh = h.hash();
        for i in 0..ecp::AESKEY {
            r[i] = sh[i]
        }
        return true;
    }
    if sha == SHA384 {
        let mut h = HASH384::new();
        h.process_array(&t);
        let sh = h.hash();
        for i in 0..ecp::AESKEY {
            r[i] = sh[i]
        }
        return true;
    }
    if sha == SHA512 {
        let mut h = HASH512::new();
        h.process_array(&t);
        let sh = h.hash();
        for i in 0..ecp::AESKEY {
            r[i] = sh[i]
        }
        return true;
    }
    return false;
}

/// Hash number (optional) and string to point on curve
fn hashit(sha: usize, n: usize, id: &[u8], w: &mut [u8]) -> bool {
    let mut r: [u8; 64] = [0; 64];
    let mut didit = false;
    if sha == SHA256 {
        let mut h = HASH256::new();
        if n > 0 {
            h.process_num(n as i32)
        }
        h.process_array(id);
        let hs = h.hash();
        for i in 0..sha {
            r[i] = hs[i];
        }
        didit = true;
    }
    if sha == SHA384 {
        let mut h = HASH384::new();
        if n > 0 {
            h.process_num(n as i32)
        }
        h.process_array(id);
        let hs = h.hash();
        for i in 0..sha {
            r[i] = hs[i];
        }
        didit = true;
    }
    if sha == SHA512 {
        let mut h = HASH512::new();
        if n > 0 {
            h.process_num(n as i32)
        }
        h.process_array(id);
        let hs = h.hash();
        for i in 0..sha {
            r[i] = hs[i];
        }
        didit = true;
    }
    if !didit {
        return false;
    }

    let rm = big::MODBYTES as usize;

    if sha > rm {
        for i in 0..rm {
            w[i] = r[i]
        }
    } else {
        for i in 0..sha {
            w[i + rm - sha] = r[i]
        }
        for i in 0..(rm - sha) {
            w[i] = 0
        }
    }

    return true;
}

/// Return time in slots since epoch
pub fn today() -> usize {
    return (SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_secs()
        / (60 * 1440)) as usize;
}

// these next two functions help to implement elligator squared - http://eprint.iacr.org/2014/043
/// Maps a random u to a point on the curve
#[allow(non_snake_case)]
fn emap(u: &Big, cb: isize) -> ECP {
    let mut P: ECP;
    let mut x = u.clone();
    let p = Big::new_ints(&rom::MODULUS);
    x.rmod(&p);
    loop {
        P = ECP::new_bigint(&x, cb);
        if !P.is_infinity() {
            break;
        }
        x.inc(1);
        x.norm();
    }
    return P;
}

/// Returns u derived from P. Random value in range 1 to return value should then be added to u
#[allow(non_snake_case)]
fn unmap(u: &mut Big, P: &mut ECP) -> isize {
    let s = P.gets();
    let mut R: ECP;
    let mut r = 0;
    let x = P.getx();
    *u = x.clone();
    loop {
        u.dec(1);
        u.norm();
        r += 1;
        R = ECP::new_bigint(u, s);
        if !R.is_infinity() {
            break;
        }
    }
    return r as isize;
}

pub fn hash_id(sha: usize, id: &[u8], w: &mut [u8]) -> bool {
    return hashit(sha, 0, id, w);
}

// These next two functions implement elligator squared - http://eprint.iacr.org/2014/043
// Elliptic curve point E in format (0x04,x,y} is converted to form {0x0-,u,v}
// Note that u and v are indistinguisible from random strings
#[allow(non_snake_case)]
pub fn encoding(rng: &mut RAND, e: &mut [u8]) -> isize {
    let mut t: [u8; EFS] = [0; EFS];

    for i in 0..EFS {
        t[i] = e[i + 1]
    }
    let mut u = Big::from_bytes(&t);
    for i in 0..EFS {
        t[i] = e[i + EFS + 1]
    }
    let mut v = Big::from_bytes(&t);

    let mut P = ECP::new_bigs(&u, &v);
    if P.is_infinity() {
        return INVALID_POINT;
    }

    let p = Big::new_ints(&rom::MODULUS);
    u = Big::randomnum(&p, rng);

    let mut su = rng.getbyte() as isize;
    su %= 2;

    let W = emap(&u, su);
    P.sub(&W);
    let sv = P.gets();
    let rn = unmap(&mut v, &mut P);
    let mut m = rng.getbyte() as isize;
    m %= rn;
    v.inc(m + 1);
    e[0] = (su + 2 * sv) as u8;
    u.to_bytes(&mut t);
    for i in 0..EFS {
        e[i + 1] = t[i]
    }
    v.to_bytes(&mut t);
    for i in 0..EFS {
        e[i + EFS + 1] = t[i]
    }

    return 0;
}

#[allow(non_snake_case)]
pub fn decoding(d: &mut [u8]) -> isize {
    let mut t: [u8; EFS] = [0; EFS];

    if (d[0] & 0x04) != 0 {
        return INVALID_POINT;
    }

    for i in 0..EFS {
        t[i] = d[i + 1]
    }
    let mut u = Big::from_bytes(&t);
    for i in 0..EFS {
        t[i] = d[i + EFS + 1]
    }
    let mut v = Big::from_bytes(&t);

    let su = (d[0] & 1) as isize;
    let sv = ((d[0] >> 1) & 1) as isize;
    let W = emap(&u, su);
    let mut P = emap(&v, sv);
    P.add(&W);
    u = P.getx();
    v = P.gety();
    d[0] = 0x04;
    u.to_bytes(&mut t);
    for i in 0..EFS {
        d[i + 1] = t[i]
    }
    v.to_bytes(&mut t);
    for i in 0..EFS {
        d[i + EFS + 1] = t[i]
    }

    return 0;
}

/// R=R1+R2 in group G1
#[allow(non_snake_case)]
pub fn recombine_g1(r1: &[u8], r2: &[u8], r: &mut [u8]) -> isize {
    let mut P = ECP::from_bytes(&r1);
    let Q = ECP::from_bytes(&r2);

    if P.is_infinity() || Q.is_infinity() {
        return INVALID_POINT;
    }

    P.add(&Q);

    P.to_bytes(r, false);
    return 0;
}

/// W=W1+W2 in group G2
#[allow(non_snake_case)]
pub fn recombine_g2(w1: &[u8], w2: &[u8], w: &mut [u8]) -> isize {
    let mut P = ECP2::from_bytes(&w1);
    let Q = ECP2::from_bytes(&w2);

    if P.is_infinity() || Q.is_infinity() {
        return INVALID_POINT;
    }

    P.add(&Q);

    P.to_bytes(w);
    return 0;
}

/// create random secret S
pub fn random_generate(rng: &mut RAND, s: &mut [u8]) -> isize {
    let r = Big::new_ints(&rom::CURVE_ORDER);
    let sc = Big::randomnum(&r, rng);
    sc.to_bytes(s);
    return 0;
}

/// Extract Server Secret SST=S*Q where Q is fixed generator in G2 and S is master secret
#[allow(non_snake_case)]
pub fn get_server_secret(s: &[u8], sst: &mut [u8]) -> isize {
    let mut Q = ECP2::generator();

    let sc = Big::from_bytes(s);
    Q = pair::g2mul(&Q, &sc);
    Q.to_bytes(sst);
    return 0;
}

/// W=x*H(G);
/// if RNG == NULL then X is passed in
/// if RNG != NULL the X is passed out
/// if type=0 W=x*G where G is point on the curve, else W=x*M(G), where M(G) is mapping of octet G to point on the curve
#[allow(non_snake_case)]
pub fn get_g1_multiple(
    rng: Option<&mut RAND>,
    typ: usize,
    x: &mut [u8],
    g: &[u8],
    w: &mut [u8],
) -> isize {
    let mut sx: Big;
    let r = Big::new_ints(&rom::CURVE_ORDER);

    if let Some(rd) = rng {
        sx = Big::randomnum(&r, rd);
        sx.to_bytes(x);
    } else {
        sx = Big::from_bytes(x);
    }
    let P: ECP;

    if typ == 0 {
        P = ECP::from_bytes(g);
        if P.is_infinity() {
            return INVALID_POINT;
        }
    } else {
        P = ECP::mapit(g)
    }

    pair::g1mul(&P, &mut sx).to_bytes(w, false);
    return 0;
}

/// Client secret CST=S*H(CID) where CID is client ID and S is master secret
/// CID is hashed externally
pub fn get_client_secret(s: &mut [u8], cid: &[u8], cst: &mut [u8]) -> isize {
    return get_g1_multiple(None, 1, s, cid, cst);
}

/// Extract PIN from TOKEN for identity CID
#[allow(non_snake_case)]
pub fn extract_pin(sha: usize, cid: &[u8], pin: i32, token: &mut [u8]) -> isize {
    return extract_factor(sha, cid, pin % MAXPIN, PBLEN, token);
}

/// Extract factor from TOKEN for identity CID
#[allow(non_snake_case)]
pub fn extract_factor(
    sha: usize,
    cid: &[u8],
    factor: i32,
    facbits: i32,
    token: &mut [u8],
) -> isize {
    let mut P = ECP::from_bytes(&token);
    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];
    if P.is_infinity() {
        return INVALID_POINT;
    }
    hashit(sha, 0, cid, &mut h);
    let mut R = ECP::mapit(&h);

    R = R.pinmul(factor, facbits);
    P.sub(&R);

    P.to_bytes(token, false);

    return 0;
}

/// Restore factor to TOKEN for identity CID
#[allow(non_snake_case)]
pub fn restore_factor(
    sha: usize,
    cid: &[u8],
    factor: i32,
    facbits: i32,
    token: &mut [u8],
) -> isize {
    let mut P = ECP::from_bytes(&token);
    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];
    if P.is_infinity() {
        return INVALID_POINT;
    }
    hashit(sha, 0, cid, &mut h);
    let mut R = ECP::mapit(&h);

    R = R.pinmul(factor, facbits);
    P.add(&R);

    P.to_bytes(token, false);

    return 0;
}

/// Functions to support M-Pin Full
#[allow(non_snake_case)]
pub fn precompute(token: &[u8], cid: &[u8], g1: &mut [u8], g2: &mut [u8]) -> isize {
    let T = ECP::from_bytes(&token);
    if T.is_infinity() {
        return INVALID_POINT;
    }

    let P = ECP::mapit(&cid);

    let Q = ECP2::generator();

    let mut g = pair::ate(&Q, &T);
    g = pair::fexp(&g);
    g.to_bytes(g1);

    g = pair::ate(&Q, &P);
    g = pair::fexp(&g);
    g.to_bytes(g2);

    return 0;
}

/// Time Permit CTT=S*(date|H(CID)) where S is master secret
#[allow(non_snake_case)]
pub fn get_client_permit(sha: usize, date: usize, s: &[u8], cid: &[u8], ctt: &mut [u8]) -> isize {
    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];
    hashit(sha, date, cid, &mut h);
    let P = ECP::mapit(&h);

    let mut sc = Big::from_bytes(s);
    pair::g1mul(&P, &mut sc).to_bytes(ctt, false);
    return 0;
}

/// Implement step 1 on client side of MPin protocol
#[allow(non_snake_case)]
pub fn client_1(
    sha: usize,
    date: usize,
    client_id: &[u8],
    rng: Option<&mut RAND>,
    x: &mut [u8],
    pin: usize,
    token: &[u8],
    sec: &mut [u8],
    xid: Option<&mut [u8]>,
    xcid: Option<&mut [u8]>,
    permit: Option<&[u8]>,
) -> isize {
    let r = Big::new_ints(&rom::CURVE_ORDER);

    let mut sx: Big;

    if let Some(rd) = rng {
        sx = Big::randomnum(&r, rd);
        sx.to_bytes(x);
    } else {
        sx = Big::from_bytes(x);
    }

    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];

    hashit(sha, 0, &client_id, &mut h);
    let mut P = ECP::mapit(&h);

    let mut T = ECP::from_bytes(&token);
    if T.is_infinity() {
        return INVALID_POINT;
    }

    let mut W = P.pinmul((pin as i32) % MAXPIN, PBLEN);
    T.add(&W);
    if date != 0 {
        if let Some(rpermit) = permit {
            W = ECP::from_bytes(&rpermit);
        }
        if W.is_infinity() {
            return INVALID_POINT;
        }
        T.add(&W);
        let mut h2: [u8; RM] = [0; RM];
        hashit(sha, date, &h, &mut h2);
        W = ECP::mapit(&h2);
        if let Some(mut rxid) = xid {
            P = pair::g1mul(&P, &mut sx);
            P.to_bytes(&mut rxid, false);
            W = pair::g1mul(&W, &mut sx);
            P.add(&W);
        } else {
            P.add(&W);
            P = pair::g1mul(&P, &mut sx);
        }
        if let Some(mut rxcid) = xcid {
            P.to_bytes(&mut rxcid, false)
        }
    } else {
        if let Some(mut rxid) = xid {
            P = pair::g1mul(&P, &mut sx);
            P.to_bytes(&mut rxid, false);
        }
    }

    T.to_bytes(sec, false);
    return 0;
}

/// Outputs H(CID) and H(T|H(CID)) for time permits. If no time permits set HID=HTID
#[allow(non_snake_case)]
pub fn server_1(sha: usize, date: usize, cid: &[u8], hid: &mut [u8], htid: Option<&mut [u8]>) {
    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];

    hashit(sha, 0, cid, &mut h);

    let mut P = ECP::mapit(&h);

    P.to_bytes(hid, false);
    if date != 0 {
        let mut h2: [u8; RM] = [0; RM];
        hashit(sha, date, &h, &mut h2);
        let R = ECP::mapit(&h2);
        P.add(&R);
        if let Some(rhtid) = htid {
            P.to_bytes(rhtid, false);
        }
    }
}

/// Implement step 2 on client side of MPin protocol
#[allow(non_snake_case)]
pub fn client_2(x: &[u8], y: &[u8], sec: &mut [u8]) -> isize {
    let r = Big::new_ints(&rom::CURVE_ORDER);
    let mut P = ECP::from_bytes(sec);
    if P.is_infinity() {
        return INVALID_POINT;
    }

    let mut px = Big::from_bytes(x);
    let py = Big::from_bytes(y);
    px.add(&py);
    px.rmod(&r);

    P = pair::g1mul(&P, &mut px);
    P.neg();
    P.to_bytes(sec, false);

    return 0;
}

/// return time since epoch
pub fn get_time() -> usize {
    return (SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_secs()) as usize;
}

/// Generate Y = H(epoch, xCID/xID)
pub fn get_y(sha: usize, timevalue: usize, xcid: &[u8], y: &mut [u8]) {
    const RM: usize = big::MODBYTES as usize;
    let mut h: [u8; RM] = [0; RM];

    hashit(sha, timevalue, xcid, &mut h);

    let mut sy = Big::from_bytes(&h);
    let q = Big::new_ints(&rom::CURVE_ORDER);
    sy.rmod(&q);
    sy.to_bytes(y);
}

/// Implement step 2 of MPin protocol on server side
#[allow(non_snake_case)]
pub fn server_2(
    date: usize,
    hid: &[u8],
    htid: Option<&[u8]>,
    y: &[u8],
    sst: &[u8],
    xid: Option<&[u8]>,
    xcid: Option<&[u8]>,
    msec: &[u8],
    e: Option<&mut [u8]>,
    f: Option<&mut [u8]>,
) -> isize {
    let Q = ECP2::generator();

    let sQ = ECP2::from_bytes(&sst);
    if sQ.is_infinity() {
        return INVALID_POINT;
    }

    let mut R: ECP;
    if date != 0 {
        if let Some(rxcid) = xcid {
            R = ECP::from_bytes(&rxcid);
        } else {
            return BAD_PARAMS;
        }
    } else {
        if let Some(rxid) = xid {
            R = ECP::from_bytes(&rxid)
        } else {
            return BAD_PARAMS;
        }
    }
    if R.is_infinity() {
        return INVALID_POINT;
    }

    let mut sy = Big::from_bytes(&y);
    let mut P: ECP;
    if date != 0 {
        if let Some(rhtid) = htid {
            P = ECP::from_bytes(&rhtid)
        } else {
            return BAD_PARAMS;
        }
    } else {
        P = ECP::from_bytes(&hid);
    }

    if P.is_infinity() {
        return INVALID_POINT;
    }

    P = pair::g1mul(&P, &mut sy);
    P.add(&R);
    R = ECP::from_bytes(&msec);
    if R.is_infinity() {
        return INVALID_POINT;
    }

    let mut g: FP12;

    g = pair::ate2(&Q, &R, &sQ, &P);
    g = pair::fexp(&g);

    if !g.is_unity() {
        if let Some(rxid) = xid {
            if let Some(re) = e {
                if let Some(rf) = f {
                    g.to_bytes(re);
                    if date != 0 {
                        P = ECP::from_bytes(&hid);
                        if P.is_infinity() {
                            return INVALID_POINT;
                        }
                        R = ECP::from_bytes(&rxid);
                        if R.is_infinity() {
                            return INVALID_POINT;
                        }
                        P = pair::g1mul(&P, &mut sy);
                        P.add(&R); //P.affine();
                    }
                    g = pair::ate(&Q, &P);
                    g = pair::fexp(&g);
                    g.to_bytes(rf);
                }
            }
        }

        return BAD_PIN;
    }

    return 0;
}

/// Pollards kangaroos used to return PIN error
pub fn kangaroo(e: &[u8], f: &[u8]) -> isize {
    let mut ge = FP12::from_bytes(e);
    let mut gf = FP12::from_bytes(f);
    let mut distance: [isize; TS] = [0; TS];
    let mut t = gf.clone();

    let mut table: Vec<FP12> = Vec::with_capacity(TS);
    let mut s: isize = 1;
    for m in 0..TS {
        distance[m] = s;
        table.push(t.clone());
        s *= 2;
        t.usqr();
    }
    t.one();
    let mut dn: isize = 0;
    let mut i: usize;
    for _ in 0..TRAP {
        i = (t.geta().geta().geta().lastbits(20) % (TS as isize)) as usize;
        t.mul(&table[i]);
        dn += distance[i];
    }
    gf = t.clone();
    gf.conj();
    let mut steps: usize = 0;
    let mut dm: isize = 0;
    let mut res: isize = 0;
    while dm - dn < MAXPIN as isize {
        steps += 1;
        if steps > 4 * TRAP {
            break;
        }
        i = (ge.geta().geta().geta().lastbits(20) % (TS as isize)) as usize;
        ge.mul(&table[i]);
        dm += distance[i];
        if ge.equals(&t) {
            res = dm - dn;
            break;
        }
        if ge.equals(&gf) {
            res = dn - dm;
            break;
        }
    }
    if steps > 4 * TRAP || dm - dn >= MAXPIN as isize {
        res = 0
    } // Trap Failed  - probable invalid token
    return res;
}

/// Hash the M-Pin transcript - new
pub fn hash_all(
    sha: usize,
    hid: &[u8],
    xid: &[u8],
    xcid: Option<&[u8]>,
    sec: &[u8],
    y: &[u8],
    r: &[u8],
    w: &[u8],
    h: &mut [u8],
) -> bool {
    let mut tlen: usize = 0;
    const RM: usize = big::MODBYTES as usize;
    let mut t: [u8; 10 * RM + 4] = [0; 10 * RM + 4];

    for i in 0..hid.len() {
        t[i] = hid[i]
    }
    tlen += hid.len();

    if let Some(rxcid) = xcid {
        for i in 0..rxcid.len() {
            t[i + tlen] = rxcid[i]
        }
        tlen += rxcid.len();
    } else {
        for i in 0..xid.len() {
            t[i + tlen] = xid[i]
        }
        tlen += xid.len();
    }

    for i in 0..sec.len() {
        t[i + tlen] = sec[i]
    }
    tlen += sec.len();
    for i in 0..y.len() {
        t[i + tlen] = y[i]
    }
    tlen += y.len();
    for i in 0..r.len() {
        t[i + tlen] = r[i]
    }
    tlen += r.len();
    for i in 0..w.len() {
        t[i + tlen] = w[i]
    }
    tlen += w.len();
    if tlen != 10 * RM + 4 {
        return false;
    }

    return hashit(sha, 0, &t, h);
}

/// Calculate common key on client side
/// wCID = w.(A+AT)
#[allow(non_snake_case)]
pub fn client_key(
    sha: usize,
    g1: &[u8],
    g2: &[u8],
    pin: usize,
    r: &[u8],
    x: &[u8],
    h: &[u8],
    wcid: &[u8],
    ck: &mut [u8],
) -> isize {
    let mut g1 = FP12::from_bytes(&g1);
    let mut g2 = FP12::from_bytes(&g2);
    let mut z = Big::from_bytes(&r);
    let mut x = Big::from_bytes(&x);
    let h = Big::from_bytes(&h);

    let mut W = ECP::from_bytes(&wcid);
    if W.is_infinity() {
        return INVALID_POINT;
    }

    W = pair::g1mul(&W, &mut x);

    let r = Big::new_ints(&rom::CURVE_ORDER);

    z.add(&h); //new
    z.rmod(&r);

    g2.pinpow(pin as i32, PBLEN);
    g1.mul(&g2);

    let mut c = g1.compow(&z, &r);

    hash(sha, &mut c, &mut W, ck);

    return 0;
}

/// calculate common key on server side
/// Z=r.A - no time permits involved
#[allow(non_snake_case)]
pub fn server_key(
    sha: usize,
    z: &[u8],
    sst: &[u8],
    w: &[u8],
    h: &[u8],
    hid: &[u8],
    xid: &[u8],
    xcid: Option<&[u8]>,
    sk: &mut [u8],
) -> isize {
    let sQ = ECP2::from_bytes(&sst);
    if sQ.is_infinity() {
        return INVALID_POINT;
    }
    let mut R = ECP::from_bytes(&z);
    if R.is_infinity() {
        return INVALID_POINT;
    }
    let mut A = ECP::from_bytes(&hid);
    if A.is_infinity() {
        return INVALID_POINT;
    }

    let mut U = if let Some(rxcid) = xcid {
        ECP::from_bytes(&rxcid)
    } else {
        ECP::from_bytes(&xid)
    };

    if U.is_infinity() {
        return INVALID_POINT;
    }

    let mut w = Big::from_bytes(&w);
    let mut h = Big::from_bytes(&h);
    A = pair::g1mul(&A, &mut h); // new
    R.add(&A);

    U = pair::g1mul(&U, &mut w);
    let mut g = pair::ate(&sQ, &R);
    g = pair::fexp(&g);

    let mut c = g.trace();

    hash(sha, &mut c, &mut U, sk);

    0
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test_utils::*;

    #[test]
    fn test_mpin_valid() {
        let mut rng = create_rng();

        pub const PERMITS: bool = true;
        pub const PINERROR: bool = true;
        pub const FULL: bool = true;

        let mut s: [u8; EGS] = [0; EGS];
        const RM: usize = EFS as usize;
        let mut hcid: [u8; RM] = [0; RM];
        let mut hsid: [u8; RM] = [0; RM];

        const G1S: usize = 2 * EFS + 1; // Group 1 Size
        const G2S: usize = 4 * EFS; // Group 2 Size
        const EAS: usize = ecp::AESKEY;

        let mut sst: [u8; G2S] = [0; G2S];
        let mut token: [u8; G1S] = [0; G1S];
        let mut permit: [u8; G1S] = [0; G1S];
        let mut g1: [u8; 12 * EFS] = [0; 12 * EFS];
        let mut g2: [u8; 12 * EFS] = [0; 12 * EFS];
        let mut xid: [u8; G1S] = [0; G1S];
        let mut xcid: [u8; G1S] = [0; G1S];
        let mut x: [u8; EGS] = [0; EGS];
        let mut y: [u8; EGS] = [0; EGS];
        let mut sec: [u8; G1S] = [0; G1S];
        let mut r: [u8; EGS] = [0; EGS];
        let mut z: [u8; G1S] = [0; G1S];
        let mut hid: [u8; G1S] = [0; G1S];
        let mut htid: [u8; G1S] = [0; G1S];
        let mut rhid: [u8; G1S] = [0; G1S];
        let mut w: [u8; EGS] = [0; EGS];
        let mut t: [u8; G1S] = [0; G1S];
        let mut e: [u8; 12 * EFS] = [0; 12 * EFS];
        let mut f: [u8; 12 * EFS] = [0; 12 * EFS];
        let mut h: [u8; RM] = [0; RM];
        let mut ck: [u8; EAS] = [0; EAS];
        let mut sk: [u8; EAS] = [0; EAS];

        let sha = ecp::HASH_TYPE;

        println!("\nTesting MPIN - PIN is 1234");
        // Trusted Authority set-up

        random_generate(&mut rng, &mut s);
        print!("Master Secret s: 0x");
        printbinary(&s);

        // Create Client Identity
        let name = "testUser@miracl.com";
        let client_id = name.as_bytes();

        print!("Client ID= ");
        printbinary(&client_id);

        hash_id(sha, &client_id, &mut hcid); // Either Client or TA calculates Hash(ID) - you decide!

        // Client and Server are issued secrets by DTA
        get_server_secret(&s, &mut sst);
        print!("Server Secret SS: 0x");
        printbinary(&sst);

        get_client_secret(&mut s, &hcid, &mut token);
        print!("Client Secret CS: 0x");
        printbinary(&token);

        // Client extracts PIN from secret to create Token
        let pin: i32 = 1234;
        println!("Client extracts PIN= {}", pin);
        let mut rtn = extract_pin(sha, &client_id, pin, &mut token);
        if rtn != 0 {
            println!("FAILURE: EXTRACT_PIN rtn: {}", rtn);
        }

        print!("Client Token TK: 0x");
        printbinary(&token);

        if FULL {
            precompute(&token, &hcid, &mut g1, &mut g2);
        }

        let mut date = 0;
        if PERMITS {
            date = today();
            // Client gets "Time Token" permit from DTA

            get_client_permit(sha, date, &s, &hcid, &mut permit);
            print!("Time Permit TP: 0x");
            printbinary(&permit);

            // This encoding makes Time permit look random - Elligator squared
            encoding(&mut rng, &mut permit);
            print!("Encoded Time Permit TP: 0x");
            printbinary(&permit);
            decoding(&mut permit);
            print!("Decoded Time Permit TP: 0x");
            printbinary(&permit);
        }

        let pin = 1234;

        println!("MPIN Multi Pass");
        // Send U=x.ID to server, and recreate secret from token and pin
        rtn = client_1(
            sha,
            date,
            &client_id,
            Some(&mut rng),
            &mut x,
            pin,
            &token,
            &mut sec,
            Some(&mut xid[..]),
            Some(&mut xcid[..]),
            Some(&permit[..]),
        );
        if rtn != 0 {
            println!("FAILURE: CLIENT_1 rtn: {}", rtn);
        }

        if FULL {
            hash_id(sha, &client_id, &mut hcid);
            get_g1_multiple(Some(&mut rng), 1, &mut r, &hcid, &mut z); // Also Send Z=r.ID to Server, remember random r
        }

        // Server calculates H(ID) and H(T|H(ID)) (if time PERMITS enabled), and maps them to points on the curve HID and HTID resp.

        server_1(sha, date, &client_id, &mut hid, Some(&mut htid[..]));

        if date != 0 {
            rhid.clone_from_slice(&htid[..]);
        } else {
            rhid.clone_from_slice(&hid[..]);
        }

        // Server generates Random number Y and sends it to Client
        random_generate(&mut rng, &mut y);

        if FULL {
            hash_id(sha, &client_id, &mut hsid);
            get_g1_multiple(Some(&mut rng), 0, &mut w, &rhid, &mut t); // Also send T=w.ID to client, remember random w
        }

        // Client Second Pass: Inputs Client secret SEC, x and y. Outputs -(x+y)*SEC
        rtn = client_2(&x, &y, &mut sec);
        if rtn != 0 {
            println!("FAILURE: CLIENT_2 rtn: {}", rtn);
        }

        // Server Second pass. Inputs hashed client id, random Y, -(x+y)*SEC, xID and xCID and Server secret SST. E and F help kangaroos to find error.
        // If PIN error not required, set E and F = null

        if !PINERROR {
            rtn = server_2(
                date,
                &hid,
                Some(&htid[..]),
                &y,
                &sst,
                Some(&xid[..]),
                Some(&xcid[..]),
                &sec,
                None,
                None,
            );
        } else {
            rtn = server_2(
                date,
                &hid,
                Some(&htid[..]),
                &y,
                &sst,
                Some(&xid[..]),
                Some(&xcid[..]),
                &sec,
                Some(&mut e),
                Some(&mut f),
            );
        }

        if rtn == BAD_PIN {
            println!("Server says - Bad Pin. I don't know you. Feck off.");
            if PINERROR {
                let err = kangaroo(&e, &f);
                if err != 0 {
                    println!("(Client PIN is out by {})", err)
                }
            }
            return;
        } else {
            println!("Server says - PIN is good! You really are {}", name);
        }

        if FULL {
            let mut pxcid = None;
            if PERMITS {
                pxcid = Some(&xcid[..])
            };

            hash_all(sha, &hcid, &xid, pxcid, &sec, &y, &z, &t, &mut h);
            client_key(sha, &g1, &g2, pin, &r, &x, &h, &t, &mut ck);
            print!("Client Key =  0x");
            printbinary(&ck);

            hash_all(sha, &hsid, &xid, pxcid, &sec, &y, &z, &t, &mut h);
            server_key(sha, &z, &sst, &w, &h, &hid, &xid, pxcid, &mut sk);
            print!("Server Key =  0x");
            printbinary(&sk);
        }
    }
}