# What kind of RSA padding mode is it?

1: I have a HTTPS server and I added hooks in RSA decryption procedure to dump error RSA input(client key exchange).

2: I get some RSA input that I couldn't check padding successfully(It's usual) and I try to decrypt manually and find some interesting RSA plaintext like this:

3: It's obvious that the plaintext is padded artificially and I want to know whether it is a attack or a known padding mode.

• The first one is missing a leading 00 byte, but the length would be non-standard with it. The first one also doesn't make sense as there doesn't seem to be a 00 delimiter. The second just looks like PKCS#1 v1.5 padding with a 48 byte payload, but without a random number generator and correct header. Are you sure you're showing us all the bytes? this looks like a mem-dump after all. – Maarten Bodewes Apr 20 '18 at 9:51
• This is definitely a deliberate input; if it is part of an attack then it might be trying to scan which TLS implementation is used by timing or interpreting the results it gets. – Maarten Bodewes Apr 20 '18 at 10:24