Struct clacc::Update

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pub struct Update<T, D = D128>where
    for<'a> T: 'a + BigInt<'a>,
    D: Map,{ /* private fields */ }

Expand description

A sum of updates to be applied to witnesses.

Implementations§

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impl<T, D> Update<T, D>where
for<'a> T: 'a + BigInt<'a>,
D: Map,

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pub fn new() -> Self

Create a new batched update.

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pub fn add<'a, V>(&mut self, v: &'a V, w: &Witness<T>)where
V: 'a + Clone + Into<Vec<u8>>,

Absorb an element that must be added to a witness.

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pub fn del<'a, V>(&mut self, v: &'a V, w: &Witness<T>)where
V: 'a + Clone + Into<Vec<u8>>,

Absorb an element that must be deleted from a witness.

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pub fn undo_add<'a, V>(&mut self, v: &'a V, w: &Witness<T>)where
V: 'a + Clone + Into<Vec<u8>>,

Undo an absorbed element’s addition into an update.

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pub fn undo_del<'a, V>(&mut self, v: &'a V, w: &Witness<T>)where
V: 'a + Clone + Into<Vec<u8>>,

Undo an absorbed element’s deletion from an update.

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pub fn update_witness<'a, V>(
&self,
acc: &Accumulator<T, D>,
v: &'a V,
w: &Witness<T>
) -> Witness<T>where
V: 'a + Clone + Into<Vec<u8>>,

Update a witness. The update will include all additions and deletions previously absorbed into this update struct.

use clacc::{Accumulator, Update, gmp::BigInt};
// In this example, the update will include a deletion, so the
// accumulator must be created with a private key.
let p = vec![0x3d];
let q = vec![0x35];
let mut acc = Accumulator::<BigInt>::with_private_key(
    p.as_slice().into(),
    q.as_slice().into(),
);
// Create the static element.
let xs = b"abc".to_vec();
// Create the deletion.
let xd = b"def".to_vec();
// Create the addition.
let xa = b"ghi".to_vec();
// Add the deletion element.
acc.add(&xd);
// Add the static element to the accumulator.
let mut wxs = acc.add(&xs);
// Delete the deletion element from the accumulator.
let wxd = acc.prove(&xd).unwrap();
acc.del(&xd, &wxd).unwrap();
// Create an update object and absorb the addition and deletion.
let mut u = Update::new();
u.del(&xd, &wxd);
u.add(&xa, &acc.add(&xa));
// Update the static element's witness.
wxs = u.update_witness(&acc, &xs, &wxs);
assert!(acc.verify(&xs, &wxs).is_ok());

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pub fn update_witnesses<'a, V, IA, IS>(
&self,
acc: &Accumulator<T, D>,
additions: Arc<Mutex<IA>>,
staticels: Arc<Mutex<IS>>
)where
V: 'a + Clone + Into<Vec<u8>>,
IA: Iterator<Item = &'a mut (V, Witness<T>)> + 'a + Send,
IS: Iterator<Item = &'a mut (V, Witness<T>)> + 'a + Send,

Thread-safe method that updates multiple witnesses.

It is assumed that the additional elements have been absorbed by the update and that their witnesses are the accumulator’s value before any of the additions or deletions absorbed by this update were applied. Updating the witnesses for each of these additional elements is thus acheived by simply removing its respective element from the update and applying the result to its witness.

This method operates on atomic references to iterators over collections of element-witness pairs. An invocation will run until the referenced iterators have reached the end of their collections. To update witnesses concurrently, simply invoke this method from multiple threads using references to the same iterators.

use clacc::{Accumulator, Update, Witness, gmp::BigInt};
use crossbeam::thread;
use num_cpus;
use rand::RngCore;
use std::sync::{Arc, Mutex};
// Create elements.
const BUCKET_SIZE: usize = 20;
const DELETIONS_COUNT: usize = 2;
const ADDITIONS_COUNT: usize = 10;
const STATICELS_COUNT: usize = BUCKET_SIZE - DELETIONS_COUNT;
let mut deletions: Vec<(Vec<u8>, Witness<BigInt>)> = vec![
    Default::default(); DELETIONS_COUNT
];
let mut additions: Vec<(Vec<u8>, Witness<BigInt>)> = vec![
    Default::default(); ADDITIONS_COUNT
];
let mut staticels: Vec<(Vec<u8>, Witness<BigInt>)> = vec![
    Default::default(); STATICELS_COUNT
];
let mut rng = rand::thread_rng();
let mut bytes = vec![0; 8];
for deletion in deletions.iter_mut() {
    rng.fill_bytes(&mut bytes);
    deletion.0 = bytes.clone();
}
for addition in additions.iter_mut() {
    rng.fill_bytes(&mut bytes);
    addition.0 = bytes.clone();
}
for staticel in staticels.iter_mut() {
    rng.fill_bytes(&mut bytes);
    staticel.0 = bytes.clone();
}
// Create accumulator with private key.
let p = vec![0x3d];
let q = vec![0x35];
let mut acc = Accumulator::<BigInt>::with_private_key(
    p.as_slice().into(),
    q.as_slice().into(),
);
// Accumulate elements.
for (element, _) in deletions.iter() {
    acc.add(element);
}
for (element, _) in staticels.iter() {
    acc.add(element);
}
// Generate witnesses for static elements.
for (element, witness) in staticels.iter_mut() {
    *witness = acc.prove(element).unwrap()
}
// Save accumulation at current state.
let prev = acc.clone();
// Accumulate deletions.
for (element, witness) in deletions.iter_mut() {
    *witness = acc.prove(element).unwrap();
    acc.del(element, witness).unwrap();
}
// Accumulate additions.
for (element, witness) in additions.iter_mut() {
    *witness = acc.add(element);
    // Use the saved accumulation as the witness value.
    witness.set_value(prev.get_value());
}
// Batch updates.
let mut update = Update::new();
for (element, witness) in deletions.iter() {
    update.del(element, witness);
}
for (element, witness) in additions.iter() {
    update.add(element, witness);
}
// Update all witnesses concurrently.
let additions_iter = Arc::new(Mutex::new(additions.iter_mut()));
let staticels_iter = Arc::new(Mutex::new(staticels.iter_mut()));
thread::scope(|scope| {
    for _ in 0..num_cpus::get() {
        let acc = acc.clone();
        let u = update.clone();
        let add = Arc::clone(&additions_iter);
        let sta = Arc::clone(&staticels_iter);
        scope.spawn(move |_| u.update_witnesses(&acc, add, sta));
    }
}).unwrap();
// Verify all updated witnesses.
for (element, witness) in additions.iter() {
    assert!(acc.verify(element, witness).is_ok());
}
for (element, witness) in staticels.iter() {
    assert!(acc.verify(element, witness).is_ok());
}