Flesh out some comments

src/ggm.rs

@@ -103,7 +103,15 @@ pub struct Credential {
 }
 
 // A submodule for issuing credentials with 5 attributes, none of which
-// are blinded to the issuer.
+// are blinded to the issuer.  We create these submodules because the
+// zero knowledge proofs (ZKPs) have to have the number of attributes
+// hardcoded.  One might imagine a Rust macro that could generate
+// submodules like these automatically, but for now, if you need a
+// different number of attributes, or different combinations of blinded
+// attributes, it is hopefully straighforward to adapt these given ones.
+// Note that "nonblind" issuing case is special: the client doesn't do a
+// ZKP at all.  The more general blinded issuing case is the next
+// submodule after this one.
 pub mod issue_nonblind_5 {
     use curve25519_dalek::ristretto::RistrettoPoint;
     use curve25519_dalek::ristretto::RistrettoBasepointTable;
@@ -386,6 +394,8 @@ pub mod issue_blind124_5 {
         let d: Scalar = Scalar::random(&mut rng);
         let D: RistrettoPoint = &d * Btable;
 
+        // Encrypt the attributes to be blinded (each times the
+        // basepoint B) to the public key we just created
         let e1: Scalar = Scalar::random(&mut rng);
         let e2: Scalar = Scalar::random(&mut rng);
         let e4: Scalar = Scalar::random(&mut rng);
@@ -586,7 +596,8 @@ pub mod issue_blind124_5 {
 }
 
 // A submodule for showing credentials with 5 attributes, blinding
-// attributes 3, 4, and 5, and displaying attributes 1 and 2.
+// attributes 3, 4, and 5, and displaying attributes 1 and 2.  As above,
+// this could possibly be generated by a Rust macro in the future.
 pub mod show_blind345_5 {
     use curve25519_dalek::ristretto::RistrettoPoint;
     use curve25519_dalek::ristretto::RistrettoBasepointTable;