Store OID in bigendian notation in pk and sk

xmss.c

@@ -16,11 +16,11 @@ int xmss_keypair(unsigned char *pk, unsigned char *sk, const uint32_t oid)
         return -1;
     }
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        pk[i] = (oid >> (8 * i)) & 0xFF;
+        pk[XMSS_OID_LEN - i - 1] = (oid >> (8 * i)) & 0xFF;
         /* For an implementation that uses runtime parameters, it is crucial
         that the OID is part of the secret key as well;
         i.e. not just for interoperability, but also for internal use. */
-        sk[i] = (oid >> (8 * i)) & 0xFF;
+        sk[XMSS_OID_LEN - i - 1] = (oid >> (8 * i)) & 0xFF;
     }
     return xmss_core_keypair(&params, pk + XMSS_OID_LEN, sk + XMSS_OID_LEN);
 }
@@ -34,7 +34,7 @@ int xmss_sign(unsigned char *sk,
     unsigned int i;
 
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        oid |= sk[i] << (i * 8);
+        oid |= sk[XMSS_OID_LEN - i - 1] << (i * 8);
     }
     if (xmss_parse_oid(&params, oid)) {
         return -1;
@@ -51,7 +51,7 @@ int xmss_sign_open(unsigned char *m, unsigned long long *mlen,
     unsigned int i;
 
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        oid |= pk[i] << (i * 8);
+        oid |= pk[XMSS_OID_LEN - i - 1] << (i * 8);
     }
     if (xmss_parse_oid(&params, oid)) {
         return -1;
@@ -68,8 +68,8 @@ int xmssmt_keypair(unsigned char *pk, unsigned char *sk, const uint32_t oid)
         return -1;
     }
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        pk[i] = (oid >> (8 * i)) & 0xFF;
-        sk[i] = (oid >> (8 * i)) & 0xFF;
+        pk[XMSS_OID_LEN - i - 1] = (oid >> (8 * i)) & 0xFF;
+        sk[XMSS_OID_LEN - i - 1] = (oid >> (8 * i)) & 0xFF;
     }
     return xmssmt_core_keypair(&params, pk + XMSS_OID_LEN, sk + XMSS_OID_LEN);
 }
@@ -83,7 +83,7 @@ int xmssmt_sign(unsigned char *sk,
     unsigned int i;
 
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        oid |= sk[i] << (i * 8);
+        oid |= sk[XMSS_OID_LEN - i - 1] << (i * 8);
     }
     if (xmssmt_parse_oid(&params, oid)) {
         return -1;
@@ -100,7 +100,7 @@ int xmssmt_sign_open(unsigned char *m, unsigned long long *mlen,
     unsigned int i;
 
     for (i = 0; i < XMSS_OID_LEN; i++) {
-        oid |= pk[i] << (i * 8);
+        oid |= pk[XMSS_OID_LEN - i - 1] << (i * 8);
     }
     if (xmssmt_parse_oid(&params, oid)) {
         return -1;