Expand CoinEnvelope to the actual two types: RSACoinEnvelope and CSCoinEnvelope, depending on the cipher

1 files changed, 25 insertions, 2 deletions

diff --git a/core/api-common.rst b/core/api-common.rst
index 6be51f49..ab7726a1 100644
--- a/core/api-common.rst
+++ b/core/api-common.rst
@@ -424,8 +424,31 @@ Blinded coin
 
 .. ts:def:: CoinEnvelope
 
-  // Blinded coin's `public EdDSA key <eddsa-coin-pub>`, `base32` encoded.
-  type CoinEnvelope = string;
+  // The type of a coin's blinded envelope depends on the cipher that is used
+  // for signing with a denomination key.
+  type CoinEnvelope = RSACoinEnvelope | CSCoinEnvelope ;
+
+.. ts:def:: RSACoinEnvelope
+
+  // For denomination signatures based on RSA, the planchet is just a blinded
+  // coin's `public EdDSA key <eddsa-coin-pub>`.
+  interface RSACoinEnvelope {
+    cipher: "RSA" | "RSA+age_restricted";
+    rsa_blinded_planchet: string;          // Crockford `Base32` encoded
+  }
+
+.. ts:def:: CSCoinEnvelope
+
+  // For denomination signatures based on Blind Clause-Schnorr, the planchet
+  // consists of the public nonce and two Curve25519 scalars which are two
+  // blinded challenges in the Blinded Clause-Schnorr signature scheme.
+  // See https://taler.net/papers/cs-thesis.pdf for details.
+  interface CSCoinEnvelope {
+    cipher: "CS" | "CS+age_restricted";
+    cs_nonce: string;      // Crockford `Base32` encoded
+    cs_blinded_c0: string; // Crockford `Base32` encoded
+    cs_blinded_c1: string; // Crockford `Base32` encoded
+  }
 
 .. ts:def:: DenominationBlindingKeyP