diff --git a/library/x509_crt.c b/library/x509_crt.c
index d9318b8322..a37e1dbafa 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -756,17 +756,22 @@ static int x509_get_authority_key_id(unsigned char **p,
     } else {
         authority_key_id->keyIdentifier.len = len;
         authority_key_id->keyIdentifier.p = *p;
+        /* Setting tag of the keyIdentfier intentionally to 0x04.
+         * Although the .keyIdentfier field is CONTEXT_SPECIFIC ([0] OPTIONAL),
+         * its tag with the content is the payload of on OCTET STRING primitive   */
         authority_key_id->keyIdentifier.tag = MBEDTLS_ASN1_OCTET_STRING;
 
         *p += len;
     }
 
     if (*p < end) {
+        /* Getting authorityCertIssuer using the required specific class tag [1] */
         if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                         MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED |
                                         1)) != 0) {
             /* authorityCertIssuer is an OPTIONAL field */
         } else {
+            /* Getting directoryName using the required specific class tag [4] */
             if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                             MBEDTLS_ASN1_CONTEXT_SPECIFIC |
                                             MBEDTLS_ASN1_CONSTRUCTED | 4)) != 0) {