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
@@ -95,7 +95,13 @@
 	checkqueue
 	coins_view
 	crypto
+	crypto_aes256
+	crypto_aes256cbc
+	crypto_chacha20
+	crypto_chacha20_poly1305_aead
 	crypto_common
+	crypto_hkdf_hmac_sha256_l32
+	crypto_poly1305
 	cuckoocache
 	descriptor_parse
 	eval_script
diff --git a/src/test/fuzz/crypto_aes256.cpp b/src/test/fuzz/crypto_aes256.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_aes256.cpp
@@ -0,0 +1,31 @@
+// 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 <crypto/aes.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cassert>
+#include <cstdint>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    const std::vector<uint8_t> key =
+        ConsumeFixedLengthByteVector(fuzzed_data_provider, AES256_KEYSIZE);
+
+    AES256Encrypt encrypt{key.data()};
+    AES256Decrypt decrypt{key.data()};
+
+    while (fuzzed_data_provider.ConsumeBool()) {
+        const std::vector<uint8_t> plaintext =
+            ConsumeFixedLengthByteVector(fuzzed_data_provider, AES_BLOCKSIZE);
+        std::vector<uint8_t> ciphertext(AES_BLOCKSIZE);
+        encrypt.Encrypt(ciphertext.data(), plaintext.data());
+        std::vector<uint8_t> decrypted_plaintext(AES_BLOCKSIZE);
+        decrypt.Decrypt(decrypted_plaintext.data(), ciphertext.data());
+        assert(decrypted_plaintext == plaintext);
+    }
+}
diff --git a/src/test/fuzz/crypto_aes256cbc.cpp b/src/test/fuzz/crypto_aes256cbc.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_aes256cbc.cpp
@@ -0,0 +1,40 @@
+// 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 <crypto/aes.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cassert>
+#include <cstdint>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    const std::vector<uint8_t> key =
+        ConsumeFixedLengthByteVector(fuzzed_data_provider, AES256_KEYSIZE);
+    const std::vector<uint8_t> iv =
+        ConsumeFixedLengthByteVector(fuzzed_data_provider, AES_BLOCKSIZE);
+    const bool pad = fuzzed_data_provider.ConsumeBool();
+
+    AES256CBCEncrypt encrypt{key.data(), iv.data(), pad};
+    AES256CBCDecrypt decrypt{key.data(), iv.data(), pad};
+
+    while (fuzzed_data_provider.ConsumeBool()) {
+        const std::vector<uint8_t> plaintext =
+            ConsumeRandomLengthByteVector(fuzzed_data_provider);
+        std::vector<uint8_t> ciphertext(plaintext.size() + AES_BLOCKSIZE);
+        const int encrypt_ret = encrypt.Encrypt(
+            plaintext.data(), plaintext.size(), ciphertext.data());
+        ciphertext.resize(encrypt_ret);
+        std::vector<uint8_t> decrypted_plaintext(ciphertext.size());
+        const int decrypt_ret = decrypt.Decrypt(
+            ciphertext.data(), ciphertext.size(), decrypted_plaintext.data());
+        decrypted_plaintext.resize(decrypt_ret);
+        assert(decrypted_plaintext == plaintext ||
+               (!pad && plaintext.size() % AES_BLOCKSIZE != 0 &&
+                encrypt_ret == 0 && decrypt_ret == 0));
+    }
+}
diff --git a/src/test/fuzz/crypto_chacha20.cpp b/src/test/fuzz/crypto_chacha20.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_chacha20.cpp
@@ -0,0 +1,60 @@
+// 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 <crypto/chacha20.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+
+    ChaCha20 chacha20;
+    if (fuzzed_data_provider.ConsumeBool()) {
+        const std::vector<uint8_t> key = ConsumeFixedLengthByteVector(
+            fuzzed_data_provider,
+            fuzzed_data_provider.ConsumeIntegralInRange<size_t>(16, 32));
+        chacha20 = ChaCha20{key.data(), key.size()};
+    }
+    while (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange(0, 4)) {
+            case 0: {
+                const std::vector<uint8_t> key = ConsumeFixedLengthByteVector(
+                    fuzzed_data_provider,
+                    fuzzed_data_provider.ConsumeIntegralInRange<size_t>(16,
+                                                                        32));
+                chacha20.SetKey(key.data(), key.size());
+                break;
+            }
+            case 1: {
+                chacha20.SetIV(
+                    fuzzed_data_provider.ConsumeIntegral<uint64_t>());
+                break;
+            }
+            case 2: {
+                chacha20.Seek(fuzzed_data_provider.ConsumeIntegral<uint64_t>());
+                break;
+            }
+            case 3: {
+                std::vector<uint8_t> output(
+                    fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0,
+                                                                        4096));
+                chacha20.Keystream(output.data(), output.size());
+                break;
+            }
+            case 4: {
+                std::vector<uint8_t> output(
+                    fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0,
+                                                                        4096));
+                const std::vector<uint8_t> input = ConsumeFixedLengthByteVector(
+                    fuzzed_data_provider, output.size());
+                chacha20.Crypt(input.data(), output.data(), input.size());
+                break;
+            }
+        }
+    }
+}
diff --git a/src/test/fuzz/crypto_chacha20_poly1305_aead.cpp b/src/test/fuzz/crypto_chacha20_poly1305_aead.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_chacha20_poly1305_aead.cpp
@@ -0,0 +1,88 @@
+// 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 <crypto/chacha_poly_aead.h>
+#include <crypto/poly1305.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cassert>
+#include <cstdint>
+#include <limits>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+
+    const std::vector<uint8_t> k1 = ConsumeFixedLengthByteVector(
+        fuzzed_data_provider, CHACHA20_POLY1305_AEAD_KEY_LEN);
+    const std::vector<uint8_t> k2 = ConsumeFixedLengthByteVector(
+        fuzzed_data_provider, CHACHA20_POLY1305_AEAD_KEY_LEN);
+
+    ChaCha20Poly1305AEAD aead(k1.data(), k1.size(), k2.data(), k2.size());
+    uint64_t seqnr_payload = 0;
+    uint64_t seqnr_aad = 0;
+    int aad_pos = 0;
+    size_t buffer_size =
+        fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096);
+    std::vector<uint8_t> in(
+        buffer_size + CHACHA20_POLY1305_AEAD_AAD_LEN + POLY1305_TAGLEN, 0);
+    std::vector<uint8_t> out(
+        buffer_size + CHACHA20_POLY1305_AEAD_AAD_LEN + POLY1305_TAGLEN, 0);
+    bool is_encrypt = fuzzed_data_provider.ConsumeBool();
+    while (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 6)) {
+            case 0: {
+                buffer_size =
+                    fuzzed_data_provider.ConsumeIntegralInRange<size_t>(64,
+                                                                        4096);
+                in = std::vector<uint8_t>(buffer_size +
+                                              CHACHA20_POLY1305_AEAD_AAD_LEN +
+                                              POLY1305_TAGLEN,
+                                          0);
+                out = std::vector<uint8_t>(buffer_size +
+                                               CHACHA20_POLY1305_AEAD_AAD_LEN +
+                                               POLY1305_TAGLEN,
+                                           0);
+                break;
+            }
+            case 1: {
+                (void)aead.Crypt(seqnr_payload, seqnr_aad, aad_pos, out.data(),
+                                 out.size(), in.data(), buffer_size,
+                                 is_encrypt);
+                break;
+            }
+            case 2: {
+                uint32_t len = 0;
+                const bool ok =
+                    aead.GetLength(&len, seqnr_aad, aad_pos, in.data());
+                assert(ok);
+                break;
+            }
+            case 3: {
+                seqnr_payload += 1;
+                aad_pos += CHACHA20_POLY1305_AEAD_AAD_LEN;
+                if (aad_pos + CHACHA20_POLY1305_AEAD_AAD_LEN >
+                    CHACHA20_ROUND_OUTPUT) {
+                    aad_pos = 0;
+                    seqnr_aad += 1;
+                }
+                break;
+            }
+            case 4: {
+                seqnr_payload = fuzzed_data_provider.ConsumeIntegral<int>();
+                break;
+            }
+            case 5: {
+                seqnr_aad = fuzzed_data_provider.ConsumeIntegral<int>();
+                break;
+            }
+            case 6: {
+                is_encrypt = fuzzed_data_provider.ConsumeBool();
+                break;
+            }
+        }
+    }
+}
diff --git a/src/test/fuzz/crypto_hkdf_hmac_sha256_l32.cpp b/src/test/fuzz/crypto_hkdf_hmac_sha256_l32.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_hkdf_hmac_sha256_l32.cpp
@@ -0,0 +1,28 @@
+// 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 <crypto/hkdf_sha256_32.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+
+    const std::vector<uint8_t> initial_key_material =
+        ConsumeRandomLengthByteVector(fuzzed_data_provider);
+
+    CHKDF_HMAC_SHA256_L32 hkdf_hmac_sha256_l32(
+        initial_key_material.data(), initial_key_material.size(),
+        fuzzed_data_provider.ConsumeRandomLengthString(1024));
+    while (fuzzed_data_provider.ConsumeBool()) {
+        std::vector<uint8_t> out(32);
+        hkdf_hmac_sha256_l32.Expand32(
+            fuzzed_data_provider.ConsumeRandomLengthString(128), out.data());
+    }
+}
diff --git a/src/test/fuzz/crypto_poly1305.cpp b/src/test/fuzz/crypto_poly1305.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/fuzz/crypto_poly1305.cpp
@@ -0,0 +1,23 @@
+// 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 <crypto/poly1305.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t> &buffer) {
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+
+    const std::vector<uint8_t> key =
+        ConsumeFixedLengthByteVector(fuzzed_data_provider, POLY1305_KEYLEN);
+    const std::vector<uint8_t> in =
+        ConsumeRandomLengthByteVector(fuzzed_data_provider);
+
+    std::vector<uint8_t> tag_out(POLY1305_TAGLEN);
+    poly1305_auth(tag_out.data(), in.data(), in.size(), key.data());
+}