diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -442,7 +442,7 @@
     if (!gArgs.GetArgs("-rpcwallet").empty()) {
         std::string walletName = gArgs.GetArg("-rpcwallet", "");
         char *encodedURI =
-            evhttp_uriencode(walletName.c_str(), walletName.size(), false);
+            evhttp_uriencode(walletName.data(), walletName.size(), false);
         if (encodedURI) {
             endpoint = "/wallet/" + std::string(encodedURI);
             free(encodedURI);
diff --git a/src/crypto/hkdf_sha256_32.cpp b/src/crypto/hkdf_sha256_32.cpp
--- a/src/crypto/hkdf_sha256_32.cpp
+++ b/src/crypto/hkdf_sha256_32.cpp
@@ -9,7 +9,7 @@
 
 CHKDF_HMAC_SHA256_L32::CHKDF_HMAC_SHA256_L32(const uint8_t *ikm, size_t ikmlen,
                                              const std::string &salt) {
-    CHMAC_SHA256((const uint8_t *)salt.c_str(), salt.size())
+    CHMAC_SHA256((const uint8_t *)salt.data(), salt.size())
         .Write(ikm, ikmlen)
         .Finalize(m_prk);
 }
diff --git a/src/fs.cpp b/src/fs.cpp
--- a/src/fs.cpp
+++ b/src/fs.cpp
@@ -125,11 +125,11 @@
 #else
     // Convert from Multi Byte to utf-16
     std::string mb_string(e.what());
-    int size = MultiByteToWideChar(CP_ACP, 0, mb_string.c_str(),
+    int size = MultiByteToWideChar(CP_ACP, 0, mb_string.data(),
                                    mb_string.size(), nullptr, 0);
 
     std::wstring utf16_string(size, L'\0');
-    MultiByteToWideChar(CP_ACP, 0, mb_string.c_str(), mb_string.size(),
+    MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(),
                         &*utf16_string.begin(), size);
     // Convert from utf-16 to utf-8
     return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>()
diff --git a/src/httprpc.cpp b/src/httprpc.cpp
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -123,9 +123,9 @@
         static const unsigned int KEY_SIZE = 32;
         uint8_t out[KEY_SIZE];
 
-        CHMAC_SHA256(reinterpret_cast<const uint8_t *>(strSalt.c_str()),
+        CHMAC_SHA256(reinterpret_cast<const uint8_t *>(strSalt.data()),
                      strSalt.size())
-            .Write(reinterpret_cast<const uint8_t *>(strPass.c_str()),
+            .Write(reinterpret_cast<const uint8_t *>(strPass.data()),
                    strPass.size())
             .Finalize(out);
         std::vector<uint8_t> hexvec(out, out + KEY_SIZE);
diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -149,7 +149,7 @@
 }
 
 std::string EncodeBase64(const std::string &str) {
-    return EncodeBase64((const uint8_t *)str.c_str(), str.size());
+    return EncodeBase64((const uint8_t *)str.data(), str.size());
 }
 
 std::vector<uint8_t> DecodeBase64(const char *p, bool *pf_invalid) {
@@ -221,7 +221,7 @@
 }
 
 std::string EncodeBase32(const std::string &str) {
-    return EncodeBase32((const uint8_t *)str.c_str(), str.size());
+    return EncodeBase32((const uint8_t *)str.data(), str.size());
 }
 
 std::vector<uint8_t> DecodeBase32(const char *p, bool *pf_invalid) {
diff --git a/src/wallet/crypter.cpp b/src/wallet/crypter.cpp
--- a/src/wallet/crypter.cpp
+++ b/src/wallet/crypter.cpp
@@ -24,7 +24,7 @@
     uint8_t buf[CSHA512::OUTPUT_SIZE];
     CSHA512 di;
 
-    di.Write((const uint8_t *)strKeyData.c_str(), strKeyData.size());
+    di.Write((const uint8_t *)strKeyData.data(), strKeyData.size());
     di.Write(chSalt.data(), chSalt.size());
     di.Finalize(buf);