diff --git a/src/test/fuzz/CMakeLists.txt b/src/test/fuzz/CMakeLists.txt
--- a/src/test/fuzz/CMakeLists.txt
+++ b/src/test/fuzz/CMakeLists.txt
@@ -87,6 +87,7 @@
 	float
 	hex
 	integer
+	key
 	net_permissions
 	p2p_transport_deserializer
 	parse_hd_keypath
diff --git a/src/test/fuzz/key.cpp b/src/test/fuzz/key.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/key.cpp
@@ -0,0 +1,342 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <chainparams.h>
+#include <chainparamsbase.h>
+#include <config.h>
+#include <key.h>
+#include <key_io.h>
+#include <outputtype.h>
+#include <policy/policy.h>
+#include <pubkey.h>
+#include <rpc/util.h>
+#include <script/keyorigin.h>
+#include <script/script.h>
+#include <script/sign.h>
+#include <script/signingprovider.h>
+#include <script/standard.h>
+#include <streams.h>
+#include <util/strencodings.h>
+
+#include <test/fuzz/fuzz.h>
+
+#include <cassert>
+#include <cstdint>
+#include <numeric>
+#include <string>
+#include <vector>
+
+void initialize() {
+    static const ECCVerifyHandle ecc_verify_handle;
+    ECC_Start();
+    SelectParams(CBaseChainParams::REGTEST);
+}
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    const CKey key = [&] {
+        CKey k;
+        k.Set(buffer.begin(), buffer.end(), true);
+        return k;
+    }();
+    if (!key.IsValid()) {
+        return;
+    }
+
+    {
+        assert(key.begin() + key.size() == key.end());
+        assert(key.IsCompressed());
+        assert(key.size() == 32);
+        assert(DecodeSecret(EncodeSecret(key)) == key);
+    }
+
+    {
+        CKey invalid_key;
+        assert(!(invalid_key == key));
+        assert(!invalid_key.IsCompressed());
+        assert(!invalid_key.IsValid());
+        assert(invalid_key.size() == 0);
+    }
+
+    {
+        CKey uncompressed_key;
+        uncompressed_key.Set(buffer.begin(), buffer.end(), false);
+        assert(!(uncompressed_key == key));
+        assert(!uncompressed_key.IsCompressed());
+        assert(key.size() == 32);
+        assert(uncompressed_key.begin() + uncompressed_key.size() ==
+               uncompressed_key.end());
+        assert(uncompressed_key.IsValid());
+    }
+
+    {
+        CKey copied_key;
+        copied_key.Set(key.begin(), key.end(), key.IsCompressed());
+        assert(copied_key == key);
+    }
+
+    {
+        CKey negated_key = key;
+        negated_key.Negate();
+        assert(negated_key.IsValid());
+        assert(!(negated_key == key));
+
+        negated_key.Negate();
+        assert(negated_key == key);
+    }
+
+    const uint256 random_uint256 = Hash(buffer.begin(), buffer.end());
+
+    {
+        CKey child_key;
+        ChainCode child_chaincode;
+        const bool ok =
+            key.Derive(child_key, child_chaincode, 0, random_uint256);
+        assert(ok);
+        assert(child_key.IsValid());
+        assert(!(child_key == key));
+        assert(child_chaincode != random_uint256);
+    }
+
+    const CPubKey pubkey = key.GetPubKey();
+
+    {
+        assert(pubkey.size() == 33);
+        assert(key.VerifyPubKey(pubkey));
+        assert(pubkey.GetHash() != random_uint256);
+        assert(pubkey.begin() + pubkey.size() == pubkey.end());
+        assert(pubkey.data() == pubkey.begin());
+        assert(pubkey.IsCompressed());
+        assert(pubkey.IsValid());
+        assert(pubkey.IsFullyValid());
+        assert(HexToPubKey(HexStr(pubkey.begin(), pubkey.end())) == pubkey);
+        assert(GetAllDestinationsForKey(pubkey).size() == 1);
+    }
+
+    {
+        CDataStream data_stream{SER_NETWORK, INIT_PROTO_VERSION};
+        pubkey.Serialize(data_stream);
+
+        CPubKey pubkey_deserialized;
+        pubkey_deserialized.Unserialize(data_stream);
+        assert(pubkey_deserialized == pubkey);
+    }
+
+    {
+        const CScript tx_pubkey_script = GetScriptForRawPubKey(pubkey);
+        assert(!tx_pubkey_script.IsPayToScriptHash());
+        assert(!tx_pubkey_script.IsPushOnly());
+        assert(!tx_pubkey_script.IsUnspendable());
+        assert(tx_pubkey_script.HasValidOps());
+        assert(tx_pubkey_script.size() == 35);
+
+        const CScript tx_multisig_script = GetScriptForMultisig(1, {pubkey});
+        assert(!tx_multisig_script.IsPayToScriptHash());
+        assert(!tx_multisig_script.IsPushOnly());
+        assert(!tx_multisig_script.IsUnspendable());
+        assert(tx_multisig_script.HasValidOps());
+        assert(tx_multisig_script.size() == 37);
+
+        FillableSigningProvider fillable_signing_provider;
+        assert(IsSolvable(fillable_signing_provider, tx_pubkey_script));
+        assert(IsSolvable(fillable_signing_provider, tx_multisig_script));
+        assert(fillable_signing_provider.GetKeys().size() == 0);
+        assert(!fillable_signing_provider.HaveKey(pubkey.GetID()));
+
+        const bool ok_add_key = fillable_signing_provider.AddKey(key);
+        assert(ok_add_key);
+        assert(fillable_signing_provider.HaveKey(pubkey.GetID()));
+
+        FillableSigningProvider fillable_signing_provider_pub;
+        assert(!fillable_signing_provider_pub.HaveKey(pubkey.GetID()));
+
+        const bool ok_add_key_pubkey =
+            fillable_signing_provider_pub.AddKeyPubKey(key, pubkey);
+        assert(ok_add_key_pubkey);
+        assert(fillable_signing_provider_pub.HaveKey(pubkey.GetID()));
+
+        txnouttype which_type_tx_pubkey;
+        const bool is_standard_tx_pubkey =
+            IsStandard(tx_pubkey_script, which_type_tx_pubkey);
+        assert(is_standard_tx_pubkey);
+        assert(which_type_tx_pubkey == txnouttype::TX_PUBKEY);
+
+        txnouttype which_type_tx_multisig;
+        const bool is_standard_tx_multisig =
+            IsStandard(tx_multisig_script, which_type_tx_multisig);
+        assert(is_standard_tx_multisig);
+        assert(which_type_tx_multisig == txnouttype::TX_MULTISIG);
+
+        std::vector<std::vector<uint8_t>> v_solutions_ret_tx_pubkey;
+        const txnouttype outtype_tx_pubkey =
+            Solver(tx_pubkey_script, v_solutions_ret_tx_pubkey);
+        assert(outtype_tx_pubkey == txnouttype::TX_PUBKEY);
+        assert(v_solutions_ret_tx_pubkey.size() == 1);
+        assert(v_solutions_ret_tx_pubkey[0].size() == 33);
+
+        std::vector<std::vector<uint8_t>> v_solutions_ret_tx_multisig;
+        const txnouttype outtype_tx_multisig =
+            Solver(tx_multisig_script, v_solutions_ret_tx_multisig);
+        assert(outtype_tx_multisig == txnouttype::TX_MULTISIG);
+        assert(v_solutions_ret_tx_multisig.size() == 3);
+        assert(v_solutions_ret_tx_multisig[0].size() == 1);
+        assert(v_solutions_ret_tx_multisig[1].size() == 33);
+        assert(v_solutions_ret_tx_multisig[2].size() == 1);
+
+        OutputType output_type{};
+        const CTxDestination tx_destination =
+            GetDestinationForKey(pubkey, output_type);
+        assert(output_type == OutputType::LEGACY);
+        assert(IsValidDestination(tx_destination));
+        assert(CTxDestination{PKHash{pubkey}} == tx_destination);
+
+        const CScript script_for_destination =
+            GetScriptForDestination(tx_destination);
+        assert(script_for_destination.size() == 25);
+
+        const Config &config = GetConfig();
+        const CChainParams &params = config.GetChainParams();
+
+        const std::string destination_address =
+            EncodeDestination(tx_destination, config);
+        assert(DecodeDestination(destination_address, params) ==
+               tx_destination);
+
+        const CPubKey pubkey_from_address_string = AddrToPubKey(
+            params, fillable_signing_provider, destination_address);
+        assert(pubkey_from_address_string == pubkey);
+
+        CKeyID key_id = pubkey.GetID();
+        assert(!key_id.IsNull());
+        assert(key_id == CKeyID{key_id});
+        assert(key_id ==
+               GetKeyForDestination(fillable_signing_provider, tx_destination));
+
+        CPubKey pubkey_out;
+        const bool ok_get_pubkey =
+            fillable_signing_provider.GetPubKey(key_id, pubkey_out);
+        assert(ok_get_pubkey);
+
+        CKey key_out;
+        const bool ok_get_key =
+            fillable_signing_provider.GetKey(key_id, key_out);
+        assert(ok_get_key);
+        assert(fillable_signing_provider.GetKeys().size() == 1);
+        assert(fillable_signing_provider.HaveKey(key_id));
+
+        KeyOriginInfo key_origin_info;
+        const bool ok_get_key_origin =
+            fillable_signing_provider.GetKeyOrigin(key_id, key_origin_info);
+        assert(!ok_get_key_origin);
+    }
+
+    {
+        const std::vector<uint8_t> vch_pubkey{pubkey.begin(), pubkey.end()};
+        assert(CPubKey::ValidSize(vch_pubkey));
+        assert(!CPubKey::ValidSize(
+            {pubkey.begin(), pubkey.begin() + pubkey.size() - 1}));
+
+        const CPubKey pubkey_ctor_1{vch_pubkey};
+        assert(pubkey == pubkey_ctor_1);
+
+        const CPubKey pubkey_ctor_2{vch_pubkey.begin(), vch_pubkey.end()};
+        assert(pubkey == pubkey_ctor_2);
+
+        CPubKey pubkey_set;
+        pubkey_set.Set(vch_pubkey.begin(), vch_pubkey.end());
+        assert(pubkey == pubkey_set);
+    }
+
+    {
+        const CPubKey invalid_pubkey{};
+        assert(!invalid_pubkey.IsValid());
+        assert(!invalid_pubkey.IsFullyValid());
+        assert(!(pubkey == invalid_pubkey));
+        assert(pubkey != invalid_pubkey);
+        assert(pubkey < invalid_pubkey);
+    }
+
+    {
+        // Cover CPubKey's operator[](unsigned int pos)
+        unsigned int sum = 0;
+        for (size_t i = 0; i < pubkey.size(); ++i) {
+            sum += pubkey[i];
+        }
+        assert(std::accumulate(pubkey.begin(), pubkey.end(), 0U) == sum);
+    }
+
+    {
+        CPubKey decompressed_pubkey = pubkey;
+        assert(decompressed_pubkey.IsCompressed());
+
+        const bool ok = decompressed_pubkey.Decompress();
+        assert(ok);
+        assert(!decompressed_pubkey.IsCompressed());
+        assert(decompressed_pubkey.size() == 65);
+    }
+
+    {
+        std::vector<uint8_t> vch_sig_ecdsa;
+        const bool ecdsa_ok =
+            key.SignECDSA(random_uint256, vch_sig_ecdsa, false);
+        assert(ecdsa_ok);
+        assert(pubkey.VerifyECDSA(random_uint256, vch_sig_ecdsa));
+        assert(CPubKey::CheckLowS(vch_sig_ecdsa));
+
+        const std::vector<uint8_t> vch_invalid_sig_ecdsa{
+            vch_sig_ecdsa.begin(),
+            vch_sig_ecdsa.begin() + vch_sig_ecdsa.size() - 1};
+        assert(!pubkey.VerifyECDSA(random_uint256, vch_invalid_sig_ecdsa));
+        assert(!CPubKey::CheckLowS(vch_invalid_sig_ecdsa));
+
+        std::vector<uint8_t> vch_sig_schnorr;
+        const bool schnorr_ok =
+            key.SignSchnorr(random_uint256, vch_sig_schnorr);
+        assert(schnorr_ok);
+        assert(vch_sig_schnorr.size() == 64);
+        assert(pubkey.VerifySchnorr(random_uint256, vch_sig_schnorr));
+
+        const std::vector<uint8_t> vch_invalid_sig_schnorr{
+            vch_sig_schnorr.begin(),
+            vch_sig_schnorr.begin() + vch_sig_schnorr.size() - 1};
+        assert(!pubkey.VerifySchnorr(random_uint256, vch_invalid_sig_schnorr));
+    }
+
+    {
+        std::vector<uint8_t> vch_compact_sig;
+        const bool ok_sign_compact =
+            key.SignCompact(random_uint256, vch_compact_sig);
+        assert(ok_sign_compact);
+
+        CPubKey recover_pubkey;
+        const bool ok_recover_compact =
+            recover_pubkey.RecoverCompact(random_uint256, vch_compact_sig);
+        assert(ok_recover_compact);
+        assert(recover_pubkey == pubkey);
+    }
+
+    {
+        CPubKey child_pubkey;
+        ChainCode child_chaincode;
+        const bool ok =
+            pubkey.Derive(child_pubkey, child_chaincode, 0, random_uint256);
+        assert(ok);
+        assert(child_pubkey != pubkey);
+        assert(child_pubkey.IsCompressed());
+        assert(child_pubkey.IsFullyValid());
+        assert(child_pubkey.IsValid());
+        assert(child_pubkey.size() == 33);
+        assert(child_chaincode != random_uint256);
+    }
+
+    const CPrivKey priv_key = key.GetPrivKey();
+
+    {
+        for (const bool skip_check : {true, false}) {
+            CKey loaded_key;
+            const bool ok = loaded_key.Load(priv_key, pubkey, skip_check);
+            assert(ok);
+            assert(key == loaded_key);
+        }
+    }
+}