diff --git a/spec/ic.did b/spec/ic.did
index 705eb6441..59bf89225 100644
--- a/spec/ic.did
+++ b/spec/ic.did
@@ -24,6 +24,19 @@ type http_response = record {
   body: blob;
 };
 
+type http_request_error = variant {
+  no_consensus;
+  timeout;
+  bad_tls;
+  invalid_url;
+  transform_error;
+  dns_error;
+  unreachable;
+  conn_timeout;
+};
+
+type ecdsa_curve = variant { secp256k1; };
+
 service ic : {
   create_canister : (record {
     settings : opt canister_settings
@@ -63,6 +76,18 @@ service ic : {
     };
   }) -> (http_response);
 
+  // Threshold ECDSA signature
+  ecdsa_public_key : (record {
+    canister_id : opt canister_id;
+    derivation_path : vec blob;
+    key_id : record { curve: ecdsa_curve; name: text };
+  }) -> (record { public_key : blob; chain_code : blob; });
+  sign_with_ecdsa : (record {
+    message_hash : blob;
+    derivation_path : vec blob;
+    key_id : record { curve: ecdsa_curve; name: text };
+  }) -> (record { signature : blob });
+
   // provisional interfaces for the pre-ledger world
   provisional_create_canister_with_cycles : (record {
     amount: opt nat;
diff --git a/spec/index.adoc b/spec/index.adoc
index a278c148a..b99c6a9e9 100644
--- a/spec/index.adoc
+++ b/spec/index.adoc
@@ -1657,6 +1657,32 @@ There is no restriction on who can invoke this method.
 
 This method takes no input and returns 32 pseudo-random bytes to the caller. The return value is unknown to any part of the IC at time of the submission of this call. A new return value is generated for each call to this method.
 
+[#ic-ecdsa_public_key]
+=== IC method `ecdsa_public_key`
+
+This method returns a https://www.secg.org/sec1-v2.pdf[SEC1] encoded ECDSA public key for the given canister using the given derivation path. If the `canister_id` is unspecified, it will default to the canister id of the caller.
+The `derivation_path` is a vector of variable length byte strings.
+The `key_id` is a struct specifying both a curve and a name.
+The availability of a particular `key_id` depends on implementation.
+
+For curve `secp256k1`, the public key is derived using a generalization of BIP32 (see https://ia.cr/2021/1330[ia.cr/2021/1330, Appendix D]). To derive (non-hardened) https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki[BIP-0032]-compatible public keys, each byte string (`blob`) in the `derivation_path` must be a 4-byte big-endian encoding of an unsigned integer less than 2^31^.
+
+The return result is an extended public key consisting of an ECDSA `public_key`, encoded in https://www.secg.org/sec2-v2.pdf[SEC1] compressed form, and a `chain_code`, which can be used to deterministically derive child keys of the `public_key`.
+
+This call requires that the ECDSA feature is enabled, and the `canister_id` meets the requirement of a canister id.
+Otherwise it will be rejected.
+
+[#ic-sign_with_ecdsa]
+=== IC method `sign_with_ecdsa`
+
+This method returns a new https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf[ECDSA] signature of the given `message_hash` that can be separately verified against a derived ECDSA public key.
+This public key can be obtained by calling `ecdsa_public_key` with the caller's `canister_id`, and the same `derivation_path` and `key_id` used here.
+
+The signatures are encoded as the concatenation of the https://www.secg.org/sec2-v2.pdf[SEC1] encodings of the two values r and s. For curve `secp256k1`, this corresponds to 32-byte big-endian encoding.
+
+This call requires that the ECDSA feature is enabled, the caller is a canister, and `message_hash` is 32 bytes long.
+Otherwise it will be rejected.
+
 [#ic-http_request]
 === IC method `http_request`