Weak cryptographic algorithms can now be disabled in Java SE 7 release. The MD2 Message-Digest Algorithm was disabled by default in Sun PKIX provider and SunJSSE provider.
The MD2 algorithm is a cryptographic hash function developed by Ronald Rivest in 1989, and was published in 1992 as an Informational RFC (RFC 1319).; RFC 6149 moves RFC 1319/MD2 to historic status, "Since its publication, MD2 has been shown to not be collision-free, albeit successful collision attacks for properly implemented MD2 are not that damaging. Successful pre-image and second pre-image attacks against MD2 have been shown."
Although MD2 is no longer considered secure, it remains in use in public key infrastructures as part of certificates generated with MD2 and RSA. An a countermeasure of the vulnerability, Java SE has disabled MD2 algorithm in certification path building and validation.
You may wonder, Java SE has disabled MD2 algorithm in certification path building and validation in the latest…
"Unrecognized_name" is an error alert, define by RFC4366. In section 4 of RFC4366:
- "unrecognized_name": this alert is sent by servers that receive a server_name extension request, but do not recognize the server name. This message MAY be fatal.
And in section 3.1 of of RFC4366:
If the server understood the client hello extension but does not recognize the server name, it SHOULD send an "unrecognized_name" alert (which MAY be fatal).
From above sections, we see that "unrecognized_name" is related to "the server name" or "server_name" extensi…