RSA AlgorithmIdentifier of X.509 Certificate
By far, RSA is a most wide used cryptography algorithm. Both ITU-T X.509 and IETF PKIX WG define the RSA algorithm identifier, however, they are not identical. ITU-T X.509[1] defines the algorithm as: rsa ALGORITHM ::= { KeySize IDENTIFIED BY id-ea-rsa } KeySize ::= INTEGER id-ea-rsa OBJECT IDENTIFIER ::= {joint-iso-itu-t(2) ds(5) algorithm(8) encryptionAlgorithm(1) rsa(1)} While IETF PKIX WG[2] defines the algorithm as: rsaPublicKey ALGORITHM-ID ::= {OID rsaEncryption PARMS NULL} rsaEncryption OBJECT IDENTIFIER ::= {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) rsaEncryption(1)} There two differences: 1. different OID. ITU-T defines it as "2.5.8.1.1", while PKIX WG defines it as "1.2.840.113549.1.1.1" 2. different algorithm parameters ITU-T defines a parameter for RSA, "KeySize", while PKIX WG defines it as null. Indeed, the RSA encryption algorithm PKIX WG u...