1  // Copyright (c) 2019-2025 Alpha-Delta Network Inc.
 2  // This file is part of the deltavm library.
 3  
 4  // Licensed under the Apache License, Version 2.0 (the "License");
 5  // you may not use this file except in compliance with the License.
 6  // You may obtain a copy of the License at:
 7  
 8  // http://www.apache.org/licenses/LICENSE-2.0
 9  
10  // Unless required by applicable law or agreed to in writing, software
11  // distributed under the License is distributed on an "AS IS" BASIS,
12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  // See the License for the specific language governing permissions and
14  // limitations under the License.
15  
16  use super::*;
17  
18  impl<A: Alpha> Record<A, Plaintext<A>> {
19      /// Encrypts `self` for the record owner under the given randomizer.
20      pub fn encrypt(&self, randomizer: &Scalar<A>) -> Record<A, Ciphertext<A>> {
21          // Output the encrypted record.
22          self.encrypt_symmetric(randomizer).0
23      }
24  
25      /// Encrypts `self` for the record owner under the given randomizer,
26      /// and returns the encrypted record alongside the record view key.
27      pub fn encrypt_symmetric(&self, randomizer: &Scalar<A>) -> (Record<A, Ciphertext<A>>, Field<A>) {
28          // Ensure the randomizer corresponds to the record nonce.
29          A::assert_eq(&self.nonce, A::g_scalar_multiply(randomizer));
30          // Compute the record view key.
31          let record_view_key = ((*self.owner).to_group() * randomizer).to_x_coordinate();
32          // Encrypt the record.
33          let encrypted_record = self.encrypt_symmetric_unchecked(record_view_key.clone());
34          // Return the encrypted record and the record view key.
35          (encrypted_record, record_view_key)
36      }
37  
38      /// Encrypts `self` under the given record view key.
39      /// Note: This method does not check that the record view key corresponds to the record owner.
40      /// Use `Self::encrypt` for the checked variant.
41      pub fn encrypt_symmetric_unchecked(&self, record_view_key: Field<A>) -> Record<A, Ciphertext<A>> {
42          // Determine the number of randomizers needed to encrypt the record.
43          let num_randomizers = self.num_randomizers();
44          // Prepare a randomizer for each field element.
45          let randomizers = A::hash_many_psd8(&[A::encryption_domain(), record_view_key], num_randomizers);
46          // Encrypt the record.
47          self.encrypt_with_randomizers(&randomizers)
48      }
49  
50      /// Encrypts `self` under the given randomizers.
51      fn encrypt_with_randomizers(&self, randomizers: &[Field<A>]) -> Record<A, Ciphertext<A>> {
52          // Initialize an index to keep track of the randomizer index.
53          let mut index: usize = 0;
54  
55          // Encrypt the owner.
56          let owner = match self.owner.is_public().eject_value() {
57              true => self.owner.encrypt(&[]),
58              false => self.owner.encrypt(&[randomizers[index].clone()]),
59          };
60  
61          // Increment the index if the owner is private.
62          if owner.is_private().eject_value() {
63              index += 1;
64          }
65  
66          // Encrypt the data.
67          let mut encrypted_data = IndexMap::with_capacity(self.data.len());
68          for (id, entry, num_randomizers) in self.data.iter().map(|(id, entry)| (id, entry, entry.num_randomizers())) {
69              // Retrieve the randomizers for this entry.
70              let randomizers = &randomizers[index..index + num_randomizers as usize];
71              // Encrypt the entry.
72              let entry = match entry {
73                  // Constant entries do not need to be encrypted.
74                  Entry::Constant(plaintext) => Entry::Constant(plaintext.clone()),
75                  // Public entries do not need to be encrypted.
76                  Entry::Public(plaintext) => Entry::Public(plaintext.clone()),
77                  // Private entries are encrypted with the given randomizers.
78                  Entry::Private(private) => Entry::Private(private.encrypt_with_randomizers(randomizers)),
79              };
80              // Insert the encrypted entry.
81              if encrypted_data.insert(id.clone(), entry).is_some() {
82                  A::halt(format!("Duplicate identifier in record: {id}"))
83              }
84              // Increment the index.
85              index += num_randomizers as usize;
86          }
87  
88          // Return the encrypted record.
89          Record { owner, data: encrypted_data, nonce: self.nonce.clone(), version: self.version.clone() }
90      }
91  }