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-rw-r--r--src/bech32.cpp8
-rw-r--r--src/bech32.h2
2 files changed, 8 insertions, 2 deletions
diff --git a/src/bech32.cpp b/src/bech32.cpp
index d6b29391a9..4c966350b4 100644
--- a/src/bech32.cpp
+++ b/src/bech32.cpp
@@ -4,6 +4,8 @@
#include <bech32.h>
+#include <assert.h>
+
namespace
{
@@ -58,7 +60,7 @@ uint32_t PolyMod(const data& v)
// During the course of the loop below, `c` contains the bitpacked coefficients of the
// polynomial constructed from just the values of v that were processed so far, mod g(x). In
- // the above example, `c` initially corresponds to 1 mod (x), and after processing 2 inputs of
+ // the above example, `c` initially corresponds to 1 mod g(x), and after processing 2 inputs of
// v, it corresponds to x^2 + v0*x + v1 mod g(x). As 1 mod g(x) = 1, that is the starting value
// for `c`.
uint32_t c = 1;
@@ -145,6 +147,10 @@ namespace bech32
/** Encode a Bech32 string. */
std::string Encode(const std::string& hrp, const data& values) {
+ // First ensure that the HRP is all lowercase. BIP-173 requires an encoder
+ // to return a lowercase Bech32 string, but if given an uppercase HRP, the
+ // result will always be invalid.
+ for (const char& c : hrp) assert(c < 'A' || c > 'Z');
data checksum = CreateChecksum(hrp, values);
data combined = Cat(values, checksum);
std::string ret = hrp + '1';
diff --git a/src/bech32.h b/src/bech32.h
index 2e2823e974..fb39cd352b 100644
--- a/src/bech32.h
+++ b/src/bech32.h
@@ -19,7 +19,7 @@
namespace bech32
{
-/** Encode a Bech32 string. Returns the empty string in case of failure. */
+/** Encode a Bech32 string. If hrp contains uppercase characters, this will cause an assertion error. */
std::string Encode(const std::string& hrp, const std::vector<uint8_t>& values);
/** Decode a Bech32 string. Returns (hrp, data). Empty hrp means failure. */