Completed credential signature data model

spec/data_flow_issuance.md

@@ -445,20 +445,13 @@ community.
 
 The credential signature elements are constructed as follows:
 
-::: todo
-
-Add the details about the credential signature data elements
-
-:::
 
-* `m_2` is the *TO BE ADDED*. It is constructed as follows:
-  * *TO BE ADDED*
-* `a` is the *TO BE ADDED*. It is constructed as follows:
-  * *TO BE ADDED*
-* `e` is the *TO BE ADDED*. It is constructed as follows:
-  * *TO BE ADDED*
-* `v` is the *TO BE ADDED*. It is constructed as follows:
-  * *TO BE ADDED*
+* `m_2` is a linkable identifier to the holder that is also called the `master_secret` in old versions. It is constructed as follows:
+  * $m_2 = H(i || \mathcal{H})$, where $i$ is an index assigned to the holder, and $\mathcal{H}$ is an identifier with which the [[ref: holder]] is known to the [[ref: issuer]].
+* `a` is the signature of the blinded known attributes. It's generation is given above.
+* `e` is a random prime generated by the [[ref: issuer]] for creating signature.
+* `v` is a number generated by the [[ref: holder]] to unblind the signature of the blinded attributes. It is constructed as follows:
+  * $v = v' + v''$, where $v'$ is the blinding factor which the holder has and $v''$ is a random number generated by the issuer.
 
 #### The Credential Signature Correctness Proof