Update readme

Signed-off-by: lovesh <[email protected]>

Author: lovesh

delg_cred_cdd/README.md

@@ -4,7 +4,7 @@
 
 ### Brief description of the API
 1. [Groth1 and Groth2 signatures](src/groth_sig.rs).  
-    - Parameters can be generated by calling `GrothS1::setup` or `GrothS2::setup`. `setup` takes the maximum nuber of attributes that need to be supported. Keep it one more than the number you want to support to accomodate the public key.
+    - Parameters can be generated by calling `GrothS1::setup` or `GrothS2::setup`. `setup` takes the maximum number of attributes that need to be supported. Keep it one more than the number you want to support to accomodate the public key.
     - Signing keys can be generated by calling `GrothS1::keygen` or `GrothS2::keygen`. Takes the corresponding setup parameters.
     - A new signature can be created by calling `Groth1Sig:new` or `Groth2Sig:new`. An existing signature can be randomized by calling `randomize` on the siganture.
     - 2 methods for signature verification, `verify` and `verify_fast`, both with the same API. `verify` computes several pairings to verify the signature whereas `verify_fast` does only 1 big multi-pairing. Applies this observation to pairings: if it needs to be cheched that a == b and c == d and e == f, then choose a random number `r` and check whether (a-b) + (c-d)*r + (e-f)*r<sup>2</sup> == 0. Refer the docs for the method for more details     
@@ -43,4 +43,4 @@ RUST_TEST_THREADS=1 cargo test --release -- --nocapture
 ```
 
 ### Pending
-1. Fix TODOs in code for more input validation and optimizations
+1. Add support for verifying the attribute token with a single multi-pairing as suggested in the TODO.

delg_cred_cdd/src/attribute_token.rs

@@ -264,9 +264,6 @@ impl<'a> AttributeToken<'a> {
                 let unrevealed_attr_count =
                     link.attribute_count() - at.odd_level_revealed_attributes[i / 2].len() - 1;
 
-                /*assert_eq!(self.blindings_t[i - 1].len(), link.signature.T.len());
-                assert_eq!(link.attribute_count(), link.signature.T.len());
-                assert_eq!(self.blindings_a[i - 1].len(), unrevealed_attr_count);*/
                 check_blindings_count!(self, i, link, unrevealed_attr_count)?;
 
                 let mut resp_t = G1Vector::with_capacity(link.attribute_count());
@@ -321,9 +318,6 @@ impl<'a> AttributeToken<'a> {
                     - at.even_level_revealed_attributes[(i / 2) - 1].len()
                     - 1;
 
-                /*assert_eq!(self.blindings_t[i - 1].len(), link.signature.T.len());
-                assert_eq!(link.attribute_count(), link.signature.T.len());
-                assert_eq!(self.blindings_a[i - 1].len(), unrevealed_attr_count);*/
                 check_blindings_count!(self, i, link, unrevealed_attr_count)?;
 
                 let mut resp_t = G2Vector::with_capacity(link.attribute_count());
@@ -732,6 +726,13 @@ impl<'a> AttributeToken<'a> {
                     GT::mul(&e_1, &e_2)
                 };
 
+                if revealed[i - 1].len() > self.setup_params_1.y.len() {
+                    return Err(DelgError::MoreAttributesThanExpected {
+                        expected: self.setup_params_1.y.len(),
+                        given: revealed[i - 1].len(),
+                    });
+                }
+
                 let unrevealed_attr_count = link.attribute_count() - revealed[i - 1].len();
                 let mut r_t = FieldElementVector::with_capacity(link.attribute_count());
                 let mut r_a = FieldElementVector::with_capacity(unrevealed_attr_count);
@@ -810,6 +811,13 @@ impl<'a> AttributeToken<'a> {
                 );
                 let com_i_s = GT::mul(&e_1, &e_2);
 
+                if revealed[i - 1].len() > self.setup_params_2.y.len() {
+                    return Err(DelgError::MoreAttributesThanExpected {
+                        expected: self.setup_params_2.y.len(),
+                        given: revealed[i - 1].len(),
+                    });
+                }
+
                 let unrevealed_attr_count = link.attribute_count() - revealed[i - 1].len();
                 let mut r_t = FieldElementVector::with_capacity(link.attribute_count());
                 let mut r_a = FieldElementVector::with_capacity(unrevealed_attr_count);

delg_cred_cdd/src/groth_sig.rs

@@ -91,7 +91,6 @@ impl GrothS1 {
     impl_GrothS_setup!(Groth1SetupParams, G1, G1Vector);
 
     pub fn keygen(setup_params: &Groth1SetupParams) -> (Groth1Sigkey, Groth1Verkey) {
-        // TODO: Take PRNG as argument
         let sk = FieldElement::random();
         let vk = &setup_params.g2 * &sk;
         (Groth1Sigkey(sk), Groth1Verkey(vk))
@@ -110,7 +109,6 @@ impl Groth1Sig {
                 given: messages.len(),
             });
         }
-        // TODO: Take PRNG as argument
         let r = FieldElement::random();
         let r_inv = r.inverse();
         let R = &setup_params.g2 * &r;
@@ -223,7 +221,6 @@ impl GrothS2 {
     impl_GrothS_setup!(Groth2SetupParams, G2, G2Vector);
 
     pub fn keygen(setup_params: &Groth2SetupParams) -> (Groth2Sigkey, Groth2Verkey) {
-        // TODO: Take PRNG as argument
         let sk = FieldElement::random();
         let vk = &setup_params.g1 * &sk;
         (Groth2Sigkey(sk), Groth2Verkey(vk))
@@ -242,7 +239,6 @@ impl Groth2Sig {
                 given: messages.len(),
             });
         }
-        // TODO: Take PRNG as argument
         let r = FieldElement::random();
         let r_inv = r.inverse();
         let R = &setup_params.g1 * &r;

delg_cred_cdd/src/issuer.rs

@@ -7,7 +7,6 @@ use amcl_wrapper::group_elem::{GroupElement, GroupElementVector};
 use amcl_wrapper::group_elem_g1::{G1LookupTable, G1Vector, G1};
 use amcl_wrapper::group_elem_g2::{G2Vector, G2};
 
-// TODO: Think about making structs rather than type alias. The struct will also hold the level
 pub type EvenLevelSigkey = Groth1Sigkey;
 pub type EvenLevelVerkey = Groth1Verkey;
 pub type OddLevelSigkey = Groth2Sigkey;
@@ -107,7 +106,6 @@ impl CredLinkEven {
 }
 
 impl CredChain {
-    // TODO: Add an iterator that traverses the links in order of level by traversing both odd_links and even_links.
     pub fn new() -> Self {
         Self {
             odd_links: vec![],