diff --git a/src/crypto/astrobwt/AstroBWT.cpp b/src/crypto/astrobwt/AstroBWT.cpp
index 5dee11657..4b3331f4b 100644
--- a/src/crypto/astrobwt/AstroBWT.cpp
+++ b/src/crypto/astrobwt/AstroBWT.cpp
@@ -86,15 +86,54 @@ static void Salsa20_XORKeyStream_AVX256(const void* key, void* output, size_t si
 }
 #endif
 
-void sort_indices(int N, const uint8_t* v, uint64_t* indices, uint64_t* tmp_indices)
+static inline bool smaller(const uint8_t* v, uint64_t a, uint64_t b)
+{
+	const uint64_t value_a = a >> 21;
+	const uint64_t value_b = b >> 21;
+
+	if (value_a < value_b) {
+		return true;
+	}
+
+	if (value_a > value_b) {
+		return false;
+	}
+
+	a &= (1 << 21) - 1;
+	b &= (1 << 21) - 1;
+
+	if (a == b) {
+		return false;
+	}
+
+	const uint64_t data_a = bswap_64(*reinterpret_cast<const uint64_t*>(v + a + 5));
+	const uint64_t data_b = bswap_64(*reinterpret_cast<const uint64_t*>(v + b + 5));
+	return (data_a < data_b);
+}
+
+void sort_indices(uint32_t N, const uint8_t* v, uint64_t* indices, uint64_t* tmp_indices)
 {
 	uint32_t counters[2][COUNTING_SORT_SIZE] = {};
 
-	for (int i = 0; i < N; ++i)
 	{
-		const uint64_t k = bswap_64(*reinterpret_cast<const uint64_t*>(v + i));
-		++counters[0][(k >> (64 - COUNTING_SORT_BITS * 2)) & (COUNTING_SORT_SIZE - 1)];
-		++counters[1][k >> (64 - COUNTING_SORT_BITS)];
+#define ITER(X) \
+		do { \
+			const uint64_t k = bswap_64(*reinterpret_cast<const uint64_t*>(v + i + X)); \
+			++counters[0][(k >> (64 - COUNTING_SORT_BITS * 2)) & (COUNTING_SORT_SIZE - 1)]; \
+			++counters[1][k >> (64 - COUNTING_SORT_BITS)]; \
+		} while (0)
+
+		uint32_t i = 0;
+		const uint32_t n = N - 15;
+		for (; i < n; i += 16) {
+			ITER(0); ITER(1); ITER(2); ITER(3); ITER(4); ITER(5); ITER(6); ITER(7);
+			ITER(8); ITER(9); ITER(10); ITER(11); ITER(12); ITER(13); ITER(14); ITER(15);
+		}
+		for (; i < N; ++i) {
+			ITER(0);
+		}
+
+#undef ITER
 	}
 
 	uint32_t prev[2] = { counters[0][0], counters[1][0] };
@@ -109,41 +148,47 @@ void sort_indices(int N, const uint8_t* v, uint64_t* indices, uint64_t* tmp_indi
 		prev[1] = cur[1];
 	}
 
-	for (int i = N - 1; i >= 0; --i)
 	{
-		const uint64_t k = bswap_64(*reinterpret_cast<const uint64_t*>(v + i));
-		tmp_indices[counters[0][(k >> (64 - COUNTING_SORT_BITS * 2)) & (COUNTING_SORT_SIZE - 1)]--] = (k & (static_cast<uint64_t>(-1) << 21)) | i;
-	}
+#define ITER(X) \
+		do { \
+			const uint64_t k = bswap_64(*reinterpret_cast<const uint64_t*>(v + (i - X))); \
+			tmp_indices[counters[0][(k >> (64 - COUNTING_SORT_BITS * 2)) & (COUNTING_SORT_SIZE - 1)]--] = (k & (static_cast<uint64_t>(-1) << 21)) | (i - X); \
+		} while (0)
 
-	for (int i = N - 1; i >= 0; --i)
-	{
-		const uint64_t data = tmp_indices[i];
-		indices[counters[1][data >> (64 - COUNTING_SORT_BITS)]--] = data;
-	}
-
-	auto smaller = [v](uint64_t a, uint64_t b)
-	{
-		const uint64_t value_a = a >> 21;
-		const uint64_t value_b = b >> 21;
-
-		if (value_a < value_b) {
-			return true;
+		uint32_t i = N;
+		for (; i >= 8; i -= 8) {
+			ITER(1); ITER(2); ITER(3); ITER(4); ITER(5); ITER(6); ITER(7); ITER(8);
+		}
+		for (; i > 0; --i) {
+			ITER(1);
 		}
 
-		if (value_a > value_b) {
-			return false;
+#undef ITER
+	}
+
+	{
+#define ITER(X) \
+		do { \
+			const uint64_t data = tmp_indices[i - X]; \
+			indices[counters[1][data >> (64 - COUNTING_SORT_BITS)]--] = data; \
+		} while (0)
+
+		uint32_t i = N;
+		for (; i >= 8; i -= 8) {
+			ITER(1); ITER(2); ITER(3); ITER(4); ITER(5); ITER(6); ITER(7); ITER(8);
+		}
+		for (; i > 0; --i) {
+			ITER(1);
 		}
 
-		const uint64_t data_a = bswap_64(*reinterpret_cast<const uint64_t*>(v + (a % (1 << 21)) + 5));
-		const uint64_t data_b = bswap_64(*reinterpret_cast<const uint64_t*>(v + (b % (1 << 21)) + 5));
-		return (data_a < data_b);
-	};
+#undef ITER
+	}
 
 	uint64_t prev_t = indices[0];
-	for (int i = 1; i < N; ++i)
+	for (uint32_t i = 1; i < N; ++i)
 	{
 		uint64_t t = indices[i];
-		if (smaller(t, prev_t))
+		if (smaller(v, t, prev_t))
 		{
 			const uint64_t t2 = prev_t;
 			int j = i - 1;
@@ -157,7 +202,7 @@ void sort_indices(int N, const uint8_t* v, uint64_t* indices, uint64_t* tmp_indi
 				}
 
 				prev_t = indices[j];
-			} while (smaller(t, prev_t));
+			} while (smaller(v, t, prev_t));
 			indices[j + 1] = t;
 			t = t2;
 		}