diff --git a/COPYRIGHT b/COPYRIGHT
index 2691795e4a..4168d62b9b 100644
--- a/COPYRIGHT
+++ b/COPYRIGHT
@@ -10,7 +10,7 @@ Copyright: © 2012-2017 Joey Hess <id@joeyh.name>
            © 2014 Sören Brunk
 License: AGPL-3+
 
-Files: Annex/AdjustedBranch.hs Annex/AdjustedBranch/Name.hs Annex/CurrentBranch.hs Annex/Version.hs Benchmark.hs Database/ContentIdentifier.hs Logs/File.hs Logs/Line.hs Logs/Smudge.hs Logs/ContentIdentifier/Pure.hs Remote/Git.hs Remote/Helper/Ssh.hs Remote/Adb.hs Remote/External.hs Remote/Extermal/Types.hs Types/AdjustedBranch.hs Types/RepoVersion.hs Upgrade/V6.hs
+Files: Annex/AdjustedBranch.hs Annex/AdjustedBranch/Name.hs Annex/CurrentBranch.hs Annex/Version.hs Benchmark.hs Database/ContentIdentifier.hs Logs/File.hs Logs/Line.hs Logs/Smudge.hs Logs/ContentIdentifier.hs Logs/ContentIdentifier/Pure.hs Remote/Git.hs Remote/Helper/Ssh.hs Remote/Adb.hs Remote/External.hs Remote/Extermal/Types.hs Types/AdjustedBranch.hs Types/RepoVersion.hs Upgrade/V6.hs
 Copyright: © 2011-2019 Joey Hess <id@joeyh.name>
 License: AGPL-3+
 
diff --git a/Logs/ContentIdentifier.hs b/Logs/ContentIdentifier.hs
new file mode 100644
index 0000000000..8329eb17c6
--- /dev/null
+++ b/Logs/ContentIdentifier.hs
@@ -0,0 +1,43 @@
+{- Remote content identifier logs.
+ -
+ - Copyright 2019 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+module Logs.ContentIdentifier (
+	recordContentIdentifier,
+	getContentIdentifiers,
+) where
+
+import Annex.Common
+import Logs
+import Logs.MapLog
+import Types.Remote (ContentIdentifier)
+import qualified Annex.Branch
+import Logs.ContentIdentifier.Pure
+import qualified Annex
+
+import qualified Data.Map as M
+
+-- | Records a remote's content identifier and the key that it corresponds to.
+--
+-- A remote may use multiple content identifiers for the same key over time,
+-- so ones that were recorded before are preserved.
+recordContentIdentifier :: UUID -> ContentIdentifier -> Key -> Annex ()
+recordContentIdentifier u cid k = do
+	c <- liftIO currentVectorClock
+	config <- Annex.getGitConfig
+	Annex.Branch.change (remoteContentIdentifierLogFile config k) $
+		buildLog . addcid c . parseLog
+  where
+	addcid c l = changeMapLog c u (cid:fromMaybe [] (M.lookup u m)) l
+	  where
+		m = simpleMap l
+
+-- | Get all content identifiers that a remote is known to use for a key.
+getContentIdentifiers :: UUID -> Key -> Annex [ContentIdentifier]
+getContentIdentifiers u k = do
+	config <- Annex.getGitConfig
+	fromMaybe [] . M.lookup u . simpleMap . parseLog
+		<$> Annex.Branch.get (remoteContentIdentifierLogFile config k)
diff --git a/git-annex.cabal b/git-annex.cabal
index 89c1f1db44..ff1e9b2249 100644
--- a/git-annex.cabal
+++ b/git-annex.cabal
@@ -870,6 +870,7 @@ Executable git-annex
     Logs.Chunk
     Logs.Chunk.Pure
     Logs.Config
+    Logs.ContentIdentifier
     Logs.ContentIdentifier.Pure
     Logs.Difference
     Logs.Difference.Pure