Hi Rajesh Bondugula,

Great details under the hood. What you have described ASN1_SHA1_MAGIC is essentially, the OID of the sha1WithRSAEncryption (1.2.840.113549.1.1.5) encoded in DER encoding. The signing operation is carried out on the DigestInfo structure as described in RFC-8017. https://tools.ietf.org/html/rfc8017. Similarly, detailed of the DER encoding can be seen in the following article: https://www.sysadmins.lv/blog-en/how-to-encode-object-identifier-to-an-asn1-der-encoded-string.aspx.