diff --git a/codex/contracts/requests.nim b/codex/contracts/requests.nim
index 48947602..448ffd63 100644
--- a/codex/contracts/requests.nim
+++ b/codex/contracts/requests.nim
@@ -29,7 +29,7 @@ type
     maxSlotLoss* {.serialize.}: uint64
 
   StorageContent* = object
-    cid* {.serialize.}: string
+    cid*: seq[byte]
     merkleRoot*: array[32, byte]
 
   Slot* = object
diff --git a/codex/node.nim b/codex/node.nim
index 2602bfe6..ef02af62 100644
--- a/codex/node.nim
+++ b/codex/node.nim
@@ -502,7 +502,7 @@ proc setupRequest(
         maxSlotLoss: tolerance,
       ),
       content: StorageContent(
-        cid: $manifestBlk.cid, # TODO: why string?
+        cid: manifestBlk.cid.data.buffer,
         merkleRoot: verifyRoot,
       ),
       expiry: expiry,
@@ -689,7 +689,7 @@ proc onProve(
     failure "Prover not enabled"
 
 proc onExpiryUpdate(
-    self: CodexNodeRef, rootCid: string, expiry: SecondsSince1970
+    self: CodexNodeRef, rootCid: seq[byte], expiry: SecondsSince1970
 ): Future[?!void] {.async.} =
   without cid =? Cid.init(rootCid):
     trace "Unable to parse Cid", cid
@@ -719,7 +719,7 @@ proc start*(self: CodexNodeRef) {.async.} =
       self.onStore(request, slot, onBatch)
 
     hostContracts.sales.onExpiryUpdate = proc(
-        rootCid: string, expiry: SecondsSince1970
+        rootCid: seq[byte], expiry: SecondsSince1970
     ): Future[?!void] =
       self.onExpiryUpdate(rootCid, expiry)
 
diff --git a/codex/sales/salescontext.nim b/codex/sales/salescontext.nim
index bb0b5dc9..128fd86f 100644
--- a/codex/sales/salescontext.nim
+++ b/codex/sales/salescontext.nim
@@ -30,7 +30,7 @@ type
   OnProve* = proc(slot: Slot, challenge: ProofChallenge): Future[?!Groth16Proof] {.
     gcsafe, upraises: []
   .}
-  OnExpiryUpdate* = proc(rootCid: string, expiry: SecondsSince1970): Future[?!void] {.
+  OnExpiryUpdate* = proc(rootCid: seq[byte], expiry: SecondsSince1970): Future[?!void] {.
     gcsafe, upraises: []
   .}
   OnClear* = proc(request: StorageRequest, slotIndex: UInt256) {.gcsafe, upraises: [].}
diff --git a/tests/codex/node/testcontracts.nim b/tests/codex/node/testcontracts.nim
index 52adb5f6..ce787ae4 100644
--- a/tests/codex/node/testcontracts.nim
+++ b/tests/codex/node/testcontracts.nim
@@ -78,7 +78,6 @@ asyncchecksuite "Test Node - Host contracts":
       erasure = Erasure.new(store, leoEncoderProvider, leoDecoderProvider, Taskpool.new)
 
     manifestCid = manifestBlock.cid
-    manifestCidStr = $(manifestCid)
 
     (await localStore.putBlock(manifestBlock)).tryGet()
 
@@ -99,7 +98,7 @@ asyncchecksuite "Test Node - Host contracts":
       expectedExpiry: SecondsSince1970 = clock.now + DefaultBlockTtl.seconds + 11123
       expiryUpdateCallback = !sales.onExpiryUpdate
 
-    (await expiryUpdateCallback(manifestCidStr, expectedExpiry)).tryGet()
+    (await expiryUpdateCallback(manifestCid.data.buffer, expectedExpiry)).tryGet()
 
     for index in 0 ..< manifest.blocksCount:
       let
@@ -116,7 +115,7 @@ asyncchecksuite "Test Node - Host contracts":
   test "onStore callback":
     let onStore = !sales.onStore
     var request = StorageRequest.example
-    request.content.cid = $verifiableBlock.cid
+    request.content.cid = verifiableBlock.cid.data.buffer
     request.expiry = (getTime() + DefaultBlockTtl.toTimesDuration + 1.hours).toUnix.u256
     var fetchedBytes: uint = 0
 
diff --git a/tests/codex/node/testnode.nim b/tests/codex/node/testnode.nim
index 3f9a141a..5058548b 100644
--- a/tests/codex/node/testnode.nim
+++ b/tests/codex/node/testnode.nim
@@ -167,7 +167,7 @@ asyncchecksuite "Test Node - Basic":
 
     check:
       (await verifiableBlock.cid in localStore) == true
-      request.content.cid == $verifiableBlock.cid
+      request.content.cid == verifiableBlock.cid.data.buffer
       request.content.merkleRoot == builder.verifyRoot.get.toBytes
 
   test "Should delete a single block":
diff --git a/tests/codex/sales/states/testfilled.nim b/tests/codex/sales/states/testfilled.nim
index f8f77da6..31fbea8b 100644
--- a/tests/codex/sales/states/testfilled.nim
+++ b/tests/codex/sales/states/testfilled.nim
@@ -36,7 +36,7 @@ checksuite "sales state 'filled'":
     market.requestEnds[request.id] = 321
     onExpiryUpdatePassedExpiry = -1
     let onExpiryUpdate = proc(
-        rootCid: string, expiry: SecondsSince1970
+        rootCid: seq[byte], expiry: SecondsSince1970
     ): Future[?!void] {.async.} =
       onExpiryUpdatePassedExpiry = expiry
       return success()
diff --git a/tests/codex/sales/testsales.nim b/tests/codex/sales/testsales.nim
index 0d441f34..484f9d79 100644
--- a/tests/codex/sales/testsales.nim
+++ b/tests/codex/sales/testsales.nim
@@ -46,7 +46,7 @@ asyncchecksuite "Sales - start":
         pricePerBytePerSecond: 1.u256,
         collateralPerByte: 1.u256,
       ),
-      content: StorageContent(cid: "some cid"),
+      content: StorageContent(cid: "some cid".toBytes),
       expiry: (getTime() + initDuration(hours = 1)).toUnix.u256,
     )
 
@@ -64,7 +64,7 @@ asyncchecksuite "Sales - start":
       return success()
 
     sales.onExpiryUpdate = proc(
-        rootCid: string, expiry: SecondsSince1970
+        rootCid: seq[byte], expiry: SecondsSince1970
     ): Future[?!void] {.async.} =
       return success()
 
@@ -158,7 +158,7 @@ asyncchecksuite "Sales":
         pricePerBytePerSecond: minPricePerBytePerSecond,
         collateralPerByte: 1.u256,
       ),
-      content: StorageContent(cid: "some cid"),
+      content: StorageContent(cid: "some cid".toBytes),
       expiry: (getTime() + initDuration(hours = 1)).toUnix.u256,
     )
 
@@ -181,7 +181,7 @@ asyncchecksuite "Sales":
       return success()
 
     sales.onExpiryUpdate = proc(
-        rootCid: string, expiry: SecondsSince1970
+        rootCid: seq[byte], expiry: SecondsSince1970
     ): Future[?!void] {.async.} =
       return success()
 
diff --git a/tests/examples.nim b/tests/examples.nim
index c96fefd6..f7680819 100644
--- a/tests/examples.nim
+++ b/tests/examples.nim
@@ -57,7 +57,7 @@ proc example*(_: type StorageRequest): StorageRequest =
       maxSlotLoss: 2, # 2 slots can be freed without data considered to be lost
     ),
     content: StorageContent(
-      cid: "zb2rhheVmk3bLks5MgzTqyznLu1zqGH5jrfTA1eAZXrjx7Vob",
+      cid: "zb2rhheVmk3bLks5MgzTqyznLu1zqGH5jrfTA1eAZXrjx7Vob".toBytes,
       merkleRoot: array[32, byte].example,
     ),
     expiry: (60 * 60).u256, # 1 hour ,
diff --git a/vendor/codex-contracts-eth b/vendor/codex-contracts-eth
index e74d3397..f1e674f9 160000
--- a/vendor/codex-contracts-eth
+++ b/vendor/codex-contracts-eth
@@ -1 +1 @@
-Subproject commit e74d3397a133eaf1eb95d9ce59f56747a7c8c30b
+Subproject commit f1e674f91c9f104bb4d7e15d4a940f755c51d818