diff --git a/src/iu_helpers.c b/src/iu_helpers.c
new file mode 100644
index 0000000..5064665
--- /dev/null
+++ b/src/iu_helpers.c
@@ -0,0 +1,48 @@
+#include <stdint.h>
+
+#include <osmocom/core/utils.h>
+
+int decode_iu_bcd(char *out, size_t out_len, const uint8_t *in, size_t in_len)
+{
+	const uint8_t *ch;
+	char *outch = out;
+
+	for (ch = in; ch < in + in_len; ch++) {
+		char c = osmo_bcd2char(*ch & 0xF);
+		*outch++ = c;
+		if (outch + 1 >= out + out_len)
+			break;
+		c = osmo_bcd2char(*ch >> 4);
+		/* skip padding nibble at end */
+		if (c == 'F')
+			break;
+		*outch++ = c;
+	}
+	*outch++ = '\0';
+	return outch - out;
+}
+
+int encode_iu_imsi(uint8_t *out, size_t out_len, const char *in)
+{
+	unsigned int len = strlen(in);
+	uint8_t odd = (len & 0x01) == 1;
+	unsigned int off = 0;
+	unsigned int i;
+
+	len /= 2;
+	if (odd)
+		len++;
+
+	for (i = 0; i < len; i++) {
+		uint8_t lower, upper;
+
+		lower = osmo_char2bcd(in[++off]) & 0x0f;
+		if (!odd && off + 1 == len)
+			upper = 0x0f;
+		else
+			upper = osmo_char2bcd(in[++off]) & 0x0f;
+
+		out[i] = (upper << 4) | lower;
+	}
+	return i;
+}