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- /*! A module for the protocol for the user to increase their trust level
- (from a level at least 1; use the trust promotion protocol to go from
- untrusted (level 0) to minimally trusted (level 1).
- They are allowed to do this as long as some amount of time (depending on
- their current level) has elapsed since their last level change, and they
- have a Bucket Reachability credential for their current bucket and
- today's date. (Such credentials are placed daily in the encrypted
- bridge table.)
- The user presents their current Lox credential:
- - id: revealed
- - bucket: blinded
- - trust_level: revealed, and must be at least 1
- - level_since: blinded, but proved in ZK that it's at least the
- appropriate number of days ago
- - invites_remaining: blinded
- - invites_issued: blinded
- and a Bucket Reachability credential:
- - date: revealed to be today
- - bucket: blinded, but proved in ZK that it's the same as in the Lox
- credential above
- and a new Lox credential to be issued:
- - id: jointly chosen by the user and BA
- - bucket: blinded, but proved in ZK that it's the same as in the Lox
- credential above
- - trust_level: revealed to be one more than the trust level above
- - level_since: today
- - invites_remaining: blinded, but proved in ZK that it's the same as in
- the Lox credential above, _plus_ a per-level constant
- - invites_issued: blinded, but proved in ZK that it's the same as in the
- Lox credential above
- */
- use curve25519_dalek::ristretto::RistrettoBasepointTable;
- use curve25519_dalek::ristretto::RistrettoPoint;
- use curve25519_dalek::scalar::Scalar;
- use curve25519_dalek::traits::IsIdentity;
- use zkp::CompactProof;
- use zkp::ProofError;
- use zkp::Transcript;
- use super::super::cred;
- use super::super::dup_filter::SeenType;
- use super::super::{pt_dbl, scalar_dbl, scalar_u32};
- use super::super::{BridgeAuth, IssuerPubKey};
- use super::super::{CMZ_A, CMZ_A_TABLE, CMZ_B, CMZ_B_TABLE};
- /// LEVEL_INTERVAL\[i\] for i >= 1 is the minimum number of days a user
- /// must be at trust level i before advancing to level i+1. The large
- /// last entry makes it impossible to advance past the top level. Note
- /// that the LEVEL_INTERVAL\[0\] entry is a dummy; the trust_promotion
- /// protocol is used instead of this one to move from level 0 to level
- /// 1.
- pub const LEVEL_INTERVAL: [u32; 5] = [0, 14, 28, 56, u32::MAX];
- /// LEVEL_INVITATIONS\[i\] for i >= 1 is the number of additional
- /// invitations a user will be eligible to issue upon advancing from
- /// level i to level i+1. Again the LEVEL_INVITATIONS\[0\] entry is a
- /// dummy, as for LEVEL_INTERVAL. Also the last entry is 0 because
- /// users cannot advance above the highest level.
- pub const LEVEL_INVITATIONS: [u32; 5] = [0, 2, 4, 6, 0];
- pub struct Request {
- // Fields for blind showing the Lox credential
- P: RistrettoPoint,
- id: Scalar,
- CBucket: RistrettoPoint,
- level: Scalar,
- CSince: RistrettoPoint,
- CInvRemain: RistrettoPoint,
- CInvIssued: RistrettoPoint,
- CQ: RistrettoPoint,
- // Fields for blind showing the Bucket Reachability credential
- P_reach: RistrettoPoint,
- CBucket_reach: RistrettoPoint,
- CQ_reach: RistrettoPoint,
- // Fields for the inequality proof (level_since +
- // LEVEL_INTERVAL[level] <= today)
- CG1: RistrettoPoint,
- CG2: RistrettoPoint,
- CG3: RistrettoPoint,
- CG4: RistrettoPoint,
- CG5: RistrettoPoint,
- CG6: RistrettoPoint,
- CG7: RistrettoPoint,
- CG8: RistrettoPoint,
- CG0sq: RistrettoPoint,
- CG1sq: RistrettoPoint,
- CG2sq: RistrettoPoint,
- CG3sq: RistrettoPoint,
- CG4sq: RistrettoPoint,
- CG5sq: RistrettoPoint,
- CG6sq: RistrettoPoint,
- CG7sq: RistrettoPoint,
- CG8sq: RistrettoPoint,
- // Fields for user blinding of the Lox credential to be issued
- D: RistrettoPoint,
- EncIdClient: (RistrettoPoint, RistrettoPoint),
- EncBucket: (RistrettoPoint, RistrettoPoint),
- EncInvRemain: (RistrettoPoint, RistrettoPoint),
- EncInvIssued: (RistrettoPoint, RistrettoPoint),
- // The combined ZKP
- piUser: CompactProof,
- }
- #[derive(Debug)]
- pub struct State {
- d: Scalar,
- D: RistrettoPoint,
- EncIdClient: (RistrettoPoint, RistrettoPoint),
- EncBucket: (RistrettoPoint, RistrettoPoint),
- EncInvRemain: (RistrettoPoint, RistrettoPoint),
- EncInvIssued: (RistrettoPoint, RistrettoPoint),
- id_client: Scalar,
- bucket: Scalar,
- level: Scalar,
- invremain: Scalar,
- invissued: Scalar,
- }
- pub struct Response {
- // The fields for the new Lox credential; the new trust level is one
- // more than the old trust level, so we don't have to include it
- // here explicitly
- P: RistrettoPoint,
- EncQ: (RistrettoPoint, RistrettoPoint),
- id_server: Scalar,
- level_since: Scalar,
- TId: RistrettoPoint,
- TBucket: RistrettoPoint,
- TInvRemain: RistrettoPoint,
- TInvIssued: RistrettoPoint,
- // The fields for the implicit noop migration ("nm") credential
- P_nm: RistrettoPoint,
- EncQ_nm: (RistrettoPoint, RistrettoPoint),
- TId_nm: RistrettoPoint,
- TBucket_nm: RistrettoPoint,
- // The ZKP
- piBlindIssue: CompactProof,
- }
- define_proof! {
- requestproof,
- "Level Upgrade Request",
- (bucket, since, invremain, invissued, zbucket, zsince, zinvremain,
- zinvissued, negzQ,
- zbucket_reach, negzQ_reach,
- d, eid_client, ebucket, einvremain, einvissued, id_client,
- g0, g1, g2, g3, g4, g5, g6, g7, g8,
- zg0, zg1, zg2, zg3, zg4, zg5, zg6, zg7, zg8,
- wg0, wg1, wg2, wg3, wg4, wg5, wg6, wg7, wg8,
- yg0, yg1, yg2, yg3, yg4, yg5, yg6, yg7, yg8),
- (P, CBucket, CSince, CInvRemain, CInvIssued, V, Xbucket, Xsince,
- Xinvremain, Xinvissued,
- P_reach, CBucket_reach, V_reach, Xbucket_reach,
- D, EncIdClient0, EncIdClient1, EncBucket0, EncBucket1,
- EncInvRemain0, EncInvRemain1_minus_LEVELINV_B,
- EncInvIssued0, EncInvIssued1,
- CG0, CG1, CG2, CG3, CG4, CG5, CG6, CG7, CG8,
- CG0sq, CG1sq, CG2sq, CG3sq, CG4sq, CG5sq, CG6sq, CG7sq, CG8sq),
- (A, B) :
- // Blind showing of the Lox credential
- CBucket = (bucket*P + zbucket*A),
- CSince = (since*P + zsince*A),
- CInvRemain = (invremain*P + zinvremain*A),
- CInvIssued = (invissued*P + zinvissued*A),
- // Blind showing of the Bucket Reachability credential; note the
- // same bucket is used in the proof
- CBucket_reach = (bucket*P_reach + zbucket_reach*A),
- // User blinding of the Lox credential to be issued
- D = (d*B),
- EncIdClient0 = (eid_client*B),
- EncIdClient1 = (id_client*B + eid_client*D),
- EncBucket0 = (ebucket*B),
- EncBucket1 = (bucket*B + ebucket*D),
- EncInvRemain0 = (einvremain*B),
- EncInvRemain1_minus_LEVELINV_B = (invremain*B + einvremain*D),
- EncInvIssued0 = (einvissued*B),
- EncInvIssued1 = (invissued*B + einvissued*D),
- // Prove CSince encodes a value at least LEVEL_INTERVAL
- // days ago (at technically at most LEVEL_INTERVAL+511 days
- // ago): first prove each of g0, ..., g8 is a bit by proving that
- // gi = gi^2
- CG0 = (g0*P + zg0*A), CG0sq = (g0*CG0 + wg0*A), CG0sq = (g0*P + yg0*A),
- CG1 = (g1*P + zg1*A), CG1sq = (g1*CG1 + wg1*A), CG1sq = (g1*P + yg1*A),
- CG2 = (g2*P + zg2*A), CG2sq = (g2*CG2 + wg2*A), CG2sq = (g2*P + yg2*A),
- CG3 = (g3*P + zg3*A), CG3sq = (g3*CG3 + wg3*A), CG3sq = (g3*P + yg3*A),
- CG4 = (g4*P + zg4*A), CG4sq = (g4*CG4 + wg4*A), CG4sq = (g4*P + yg4*A),
- CG5 = (g5*P + zg5*A), CG5sq = (g5*CG5 + wg5*A), CG5sq = (g5*P + yg5*A),
- CG6 = (g6*P + zg6*A), CG6sq = (g6*CG6 + wg6*A), CG6sq = (g6*P + yg6*A),
- CG7 = (g7*P + zg7*A), CG7sq = (g7*CG7 + wg7*A), CG7sq = (g7*P + yg7*A),
- CG8 = (g8*P + zg8*A), CG8sq = (g8*CG8 + wg8*A), CG8sq = (g8*P + yg8*A)
- // Then we'll check that CSince + LEVEL_INTERVAL*P + CG0 + 2*CG1
- // + 4*CG2 + 8*CG3 + ... + 256*CG8 = today*P by having the verifier
- // plug in today*P - (CSince + LEVEL_INTERVAL*P + 2*CG1 + 4*CG2
- // + ... + 256*CG8) as its value of CG0.
- }
- pub fn request(
- lox_cred: &cred::Lox,
- reach_cred: &cred::BucketReachability,
- lox_pub: &IssuerPubKey,
- reach_pub: &IssuerPubKey,
- today: u32,
- ) -> Result<(Request, State), ProofError> {
- let A: &RistrettoPoint = &CMZ_A;
- let B: &RistrettoPoint = &CMZ_B;
- let Atable: &RistrettoBasepointTable = &CMZ_A_TABLE;
- let Btable: &RistrettoBasepointTable = &CMZ_B_TABLE;
- // Ensure the credential can be correctly shown: it must be the case
- // that level_since + LEVEL_INTERVAL[level] <= today.
- let level_since: u32 = match scalar_u32(&lox_cred.level_since) {
- Some(v) => v,
- None => return Err(ProofError::VerificationFailure),
- };
- // The trust level has to be at least 1
- let trust_level: u32 = match scalar_u32(&lox_cred.trust_level) {
- Some(v) => v,
- None => return Err(ProofError::VerificationFailure),
- };
- if trust_level < 1 {
- return Err(ProofError::VerificationFailure);
- }
- // The trust level has to be no higher than the highest level
- let level_interval: u32 = match LEVEL_INTERVAL.get(trust_level as usize) {
- Some(&v) => v,
- None => return Err(ProofError::VerificationFailure),
- };
- if level_since + level_interval > today {
- return Err(ProofError::VerificationFailure);
- }
- // The credential can't be _too_ old
- let diffdays = today - (level_since + level_interval);
- if diffdays > 511 {
- return Err(ProofError::VerificationFailure);
- }
- // The buckets in the Lox and Bucket Reachability credentials have
- // to match
- if lox_cred.bucket != reach_cred.bucket {
- return Err(ProofError::VerificationFailure);
- }
- // The Bucket Reachability credential has to be dated today
- let reach_date: u32 = match scalar_u32(&reach_cred.date) {
- Some(v) => v,
- None => return Err(ProofError::VerificationFailure),
- };
- if reach_date != today {
- return Err(ProofError::VerificationFailure);
- }
- // Blind showing the Lox credential
- // Reblind P and Q
- let mut rng = rand::thread_rng();
- let t = Scalar::random(&mut rng);
- let P = t * lox_cred.P;
- let Q = t * lox_cred.Q;
- // Form Pedersen commitments to the blinded attributes
- let zbucket = Scalar::random(&mut rng);
- let zsince = Scalar::random(&mut rng);
- let zinvremain = Scalar::random(&mut rng);
- let zinvissued = Scalar::random(&mut rng);
- let CBucket = lox_cred.bucket * P + &zbucket * Atable;
- let CSince = lox_cred.level_since * P + &zsince * Atable;
- let CInvRemain = lox_cred.invites_remaining * P + &zinvremain * Atable;
- let CInvIssued = lox_cred.invites_issued * P + &zinvissued * Atable;
- // Form a Pedersen commitment to the MAC Q
- // We flip the sign of zQ from that of the Hyphae paper so that
- // the ZKP has a "+" instead of a "-", as that's what the zkp
- // macro supports.
- let negzQ = Scalar::random(&mut rng);
- let CQ = Q - &negzQ * Atable;
- // Compute the "error factor"
- let V = zbucket * lox_pub.X[2]
- + zsince * lox_pub.X[4]
- + zinvremain * lox_pub.X[5]
- + zinvissued * lox_pub.X[6]
- + &negzQ * Atable;
- // Blind showing the Bucket Reachability credential
- // Reblind P and Q
- let t_reach = Scalar::random(&mut rng);
- let P_reach = t_reach * reach_cred.P;
- let Q_reach = t_reach * reach_cred.Q;
- // Form Pedersen commitments to the blinded attributes
- let zbucket_reach = Scalar::random(&mut rng);
- let CBucket_reach = reach_cred.bucket * P_reach + &zbucket_reach * Atable;
- // Form a Pedersen commitment to the MAC Q
- // We flip the sign of zQ from that of the Hyphae paper so that
- // the ZKP has a "+" instead of a "-", as that's what the zkp
- // macro supports.
- let negzQ_reach = Scalar::random(&mut rng);
- let CQ_reach = Q_reach - &negzQ_reach * Atable;
- // Compute the "error factor"
- let V_reach = zbucket_reach * reach_pub.X[2] + &negzQ_reach * Atable;
- // User blinding for the Lox certificate to be issued
- // Pick an ElGamal keypair
- let d = Scalar::random(&mut rng);
- let D = &d * Btable;
- // Pick a random client component of the id
- let id_client = Scalar::random(&mut rng);
- // Encrypt it (times the basepoint B) to the ElGamal public key D we
- // just created
- let eid_client = Scalar::random(&mut rng);
- let EncIdClient = (&eid_client * Btable, &id_client * Btable + eid_client * D);
- // Encrypt the other blinded fields (times B) to D as well
- let ebucket = Scalar::random(&mut rng);
- let EncBucket = (&ebucket * Btable, &lox_cred.bucket * Btable + ebucket * D);
- let newinvites: Scalar = LEVEL_INVITATIONS[trust_level as usize].into();
- let einvremain = Scalar::random(&mut rng);
- let EncInvRemain = (
- &einvremain * Btable,
- &(lox_cred.invites_remaining + newinvites) * Btable + einvremain * D,
- );
- let einvissued = Scalar::random(&mut rng);
- let EncInvIssued = (
- &einvissued * Btable,
- &lox_cred.invites_issued * Btable + einvissued * D,
- );
- // The range proof that 0 <= diffdays <= 511
- // Extract the 9 bits from diffdays
- let g0: Scalar = (diffdays & 1).into();
- let g1: Scalar = ((diffdays >> 1) & 1).into();
- let g2: Scalar = ((diffdays >> 2) & 1).into();
- let g3: Scalar = ((diffdays >> 3) & 1).into();
- let g4: Scalar = ((diffdays >> 4) & 1).into();
- let g5: Scalar = ((diffdays >> 5) & 1).into();
- let g6: Scalar = ((diffdays >> 6) & 1).into();
- let g7: Scalar = ((diffdays >> 7) & 1).into();
- let g8: Scalar = ((diffdays >> 8) & 1).into();
- // Pick random factors for the Pedersen commitments
- let wg0 = Scalar::random(&mut rng);
- let zg1 = Scalar::random(&mut rng);
- let wg1 = Scalar::random(&mut rng);
- let zg2 = Scalar::random(&mut rng);
- let wg2 = Scalar::random(&mut rng);
- let zg3 = Scalar::random(&mut rng);
- let wg3 = Scalar::random(&mut rng);
- let zg4 = Scalar::random(&mut rng);
- let wg4 = Scalar::random(&mut rng);
- let zg5 = Scalar::random(&mut rng);
- let wg5 = Scalar::random(&mut rng);
- let zg6 = Scalar::random(&mut rng);
- let wg6 = Scalar::random(&mut rng);
- let zg7 = Scalar::random(&mut rng);
- let wg7 = Scalar::random(&mut rng);
- let zg8 = Scalar::random(&mut rng);
- let wg8 = Scalar::random(&mut rng);
- // Compute zg0 to cancel things out as
- // zg0 = -(zsince + 2*zg1 + 4*zg2 + 8*zg3 + 16*zg4 + 32*zg5 + 64*zg6 + 128*zg7 + 256*zg8)
- // but use Horner's method
- let zg0 = -(scalar_dbl(
- &(scalar_dbl(
- &(scalar_dbl(
- &(scalar_dbl(
- &(scalar_dbl(
- &(scalar_dbl(&(scalar_dbl(&(scalar_dbl(&zg8) + zg7)) + zg6)) + zg5),
- ) + zg4),
- ) + zg3),
- ) + zg2),
- ) + zg1),
- ) + zsince);
- let yg0 = wg0 + g0 * zg0;
- let yg1 = wg1 + g1 * zg1;
- let yg2 = wg2 + g2 * zg2;
- let yg3 = wg3 + g3 * zg3;
- let yg4 = wg4 + g4 * zg4;
- let yg5 = wg5 + g5 * zg5;
- let yg6 = wg6 + g6 * zg6;
- let yg7 = wg7 + g7 * zg7;
- let yg8 = wg8 + g8 * zg8;
- let CG0 = g0 * P + &zg0 * Atable;
- let CG1 = g1 * P + &zg1 * Atable;
- let CG2 = g2 * P + &zg2 * Atable;
- let CG3 = g3 * P + &zg3 * Atable;
- let CG4 = g4 * P + &zg4 * Atable;
- let CG5 = g5 * P + &zg5 * Atable;
- let CG6 = g6 * P + &zg6 * Atable;
- let CG7 = g7 * P + &zg7 * Atable;
- let CG8 = g8 * P + &zg8 * Atable;
- let CG0sq = g0 * P + &yg0 * Atable;
- let CG1sq = g1 * P + &yg1 * Atable;
- let CG2sq = g2 * P + &yg2 * Atable;
- let CG3sq = g3 * P + &yg3 * Atable;
- let CG4sq = g4 * P + &yg4 * Atable;
- let CG5sq = g5 * P + &yg5 * Atable;
- let CG6sq = g6 * P + &yg6 * Atable;
- let CG7sq = g7 * P + &yg7 * Atable;
- let CG8sq = g8 * P + &yg8 * Atable;
- // Construct the proof
- let mut transcript = Transcript::new(b"level upgrade request");
- let piUser = requestproof::prove_compact(
- &mut transcript,
- requestproof::ProveAssignments {
- A: &A,
- B: &B,
- P: &P,
- CBucket: &CBucket,
- CSince: &CSince,
- CInvRemain: &CInvRemain,
- CInvIssued: &CInvIssued,
- V: &V,
- Xbucket: &lox_pub.X[2],
- Xsince: &lox_pub.X[4],
- Xinvremain: &lox_pub.X[5],
- Xinvissued: &lox_pub.X[6],
- P_reach: &P_reach,
- CBucket_reach: &CBucket_reach,
- V_reach: &V_reach,
- Xbucket_reach: &reach_pub.X[2],
- D: &D,
- EncIdClient0: &EncIdClient.0,
- EncIdClient1: &EncIdClient.1,
- EncBucket0: &EncBucket.0,
- EncBucket1: &EncBucket.1,
- EncInvRemain0: &EncInvRemain.0,
- EncInvRemain1_minus_LEVELINV_B: &(EncInvRemain.1 - &newinvites * Btable),
- EncInvIssued0: &EncInvIssued.0,
- EncInvIssued1: &EncInvIssued.1,
- CG0: &CG0,
- CG1: &CG1,
- CG2: &CG2,
- CG3: &CG3,
- CG4: &CG4,
- CG5: &CG5,
- CG6: &CG6,
- CG7: &CG7,
- CG8: &CG8,
- CG0sq: &CG0sq,
- CG1sq: &CG1sq,
- CG2sq: &CG2sq,
- CG3sq: &CG3sq,
- CG4sq: &CG4sq,
- CG5sq: &CG5sq,
- CG6sq: &CG6sq,
- CG7sq: &CG7sq,
- CG8sq: &CG8sq,
- bucket: &lox_cred.bucket,
- since: &lox_cred.level_since,
- invremain: &lox_cred.invites_remaining,
- invissued: &lox_cred.invites_issued,
- zbucket: &zbucket,
- zsince: &zsince,
- zinvremain: &zinvremain,
- zinvissued: &zinvissued,
- negzQ: &negzQ,
- zbucket_reach: &zbucket_reach,
- negzQ_reach: &negzQ_reach,
- d: &d,
- eid_client: &eid_client,
- ebucket: &ebucket,
- einvremain: &einvremain,
- einvissued: &einvissued,
- id_client: &id_client,
- g0: &g0,
- g1: &g1,
- g2: &g2,
- g3: &g3,
- g4: &g4,
- g5: &g5,
- g6: &g6,
- g7: &g7,
- g8: &g8,
- zg0: &zg0,
- zg1: &zg1,
- zg2: &zg2,
- zg3: &zg3,
- zg4: &zg4,
- zg5: &zg5,
- zg6: &zg6,
- zg7: &zg7,
- zg8: &zg8,
- wg0: &wg0,
- wg1: &wg1,
- wg2: &wg2,
- wg3: &wg3,
- wg4: &wg4,
- wg5: &wg5,
- wg6: &wg6,
- wg7: &wg7,
- wg8: &wg8,
- yg0: &yg0,
- yg1: &yg1,
- yg2: &yg2,
- yg3: &yg3,
- yg4: &yg4,
- yg5: &yg5,
- yg6: &yg6,
- yg7: &yg7,
- yg8: &yg8,
- },
- )
- .0;
- Ok((
- Request {
- P,
- id: lox_cred.id,
- CBucket,
- level: lox_cred.trust_level,
- CSince,
- CInvRemain,
- CInvIssued,
- CQ,
- P_reach,
- CBucket_reach,
- CQ_reach,
- D,
- EncIdClient,
- EncBucket,
- EncInvRemain,
- EncInvIssued,
- CG1,
- CG2,
- CG3,
- CG4,
- CG5,
- CG6,
- CG7,
- CG8,
- CG0sq,
- CG1sq,
- CG2sq,
- CG3sq,
- CG4sq,
- CG5sq,
- CG6sq,
- CG7sq,
- CG8sq,
- piUser,
- },
- State {
- d,
- D,
- EncIdClient,
- EncBucket,
- EncInvRemain,
- EncInvIssued,
- id_client,
- bucket: lox_cred.bucket,
- level: lox_cred.trust_level + Scalar::one(),
- invremain: lox_cred.invites_remaining + newinvites,
- invissued: lox_cred.invites_issued,
- },
- ))
- }
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