diff --git a/src/base58.h b/src/base58.h
--- a/src/base58.h
+++ b/src/base58.h
@@ -26,14 +26,6 @@
  */
 std::string EncodeBase58(Span<const uint8_t> input);
 
-/**
- * Decode a base58-encoded string (psz) into a byte vector (vchRet).
- * return true if decoding is successful.
- * psz cannot be nullptr.
- */
-[[nodiscard]] bool DecodeBase58(const char *psz, std::vector<uint8_t> &vchRet,
-                                int max_ret_len);
-
 /**
  * Decode a base58-encoded string (str) into a byte vector (vchRet).
  * return true if decoding is successful.
@@ -46,14 +38,6 @@
  */
 std::string EncodeBase58Check(Span<const uint8_t> input);
 
-/**
- * Decode a base58-encoded string (psz) that includes a checksum into a byte
- * vector (vchRet), return true if decoding is successful
- */
-[[nodiscard]] bool DecodeBase58Check(const char *psz,
-                                     std::vector<uint8_t> &vchRet,
-                                     int max_ret_len);
-
 /**
  * Decode a base58-encoded string (str) that includes a checksum into a byte
  * vector (vchRet), return true if decoding is successful
diff --git a/src/base58.cpp b/src/base58.cpp
--- a/src/base58.cpp
+++ b/src/base58.cpp
@@ -34,7 +34,8 @@
     -1, -1, -1, -1, -1, -1, -1, -1, -1,
 };
 
-bool DecodeBase58(const char *psz, std::vector<uint8_t> &vch, int max_ret_len) {
+[[nodiscard]] static bool
+DecodeBase58(const char *psz, std::vector<uint8_t> &vch, int max_ret_len) {
     // Skip leading spaces.
     while (*psz && IsSpace(*psz)) {
         psz++;
@@ -156,8 +157,9 @@
     return EncodeBase58(vch);
 }
 
-bool DecodeBase58Check(const char *psz, std::vector<uint8_t> &vchRet,
-                       int max_ret_len) {
+[[nodiscard]] static bool DecodeBase58Check(const char *psz,
+                                            std::vector<uint8_t> &vchRet,
+                                            int max_ret_len) {
     if (!DecodeBase58(psz, vchRet,
                       max_ret_len > std::numeric_limits<int>::max() - 4
                           ? std::numeric_limits<int>::max()