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zkvm/docs/import-spec.md

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+# Importing assets from Stellar to ZkVM
+
+This protocol defines the process of importing of assets originally issued on the Stellar into ZkVM and exporting them back to the Stellar network.
+
+The protocol uses _trusted custodian_ secured with multi-signatures and stateless validation (only the blockchain state is used).
+
+## Importing assets
+
+TBD:
+
+## Exporting assets
+
+TBD:
+
+## Asset to flavor mapping
+
+To map the stellar asset, we will use `metadata` argument that represents an XDR-encoded `Asset` structure
+as specified in the `Stellar-ledger-entries.x` XDR file:
+
+```
+namespace stellar {
+	typedef PublicKey AccountID;
+	...
+	typedef opaque AssetCode4[4];
+	typedef opaque AssetCode12[12];
+
+	enum AssetType {
+	    ASSET_TYPE_NATIVE = 0,
+	    ASSET_TYPE_CREDIT_ALPHANUM4 = 1,
+	    ASSET_TYPE_CREDIT_ALPHANUM12 = 2
+	};
+
+	union Asset switch (AssetType type) {
+		case ASSET_TYPE_NATIVE: void;
+		case ASSET_TYPE_CREDIT_ALPHANUM4:
+		    struct {
+		        AssetCode4 assetCode;
+		        AccountID issuer;
+		    } alphaNum4;
+		case ASSET_TYPE_CREDIT_ALPHANUM12:
+		    struct {
+		        AssetCode12 assetCode;
+		        AccountID issuer;
+		    } alphaNum12;
+	};
+}
+```
+
+The resulting _flavor scalar_ is therefore formed as any other flavor, as a combination of the ZkVM issuer (custodian) key and the metadata identifying the Stellar asset.
+
+See also [ZkVM `issue` documentation](zkvm-spec.md#issue).