bitcoind uses (256-bit) ecdsa keys, so i would expect the bleeding of signing key via prime factors, which is specific to rsa, to be irrelevant.
i could, of course, be wrong
i could, of course, be wrong
Blind signatures, as described by David Chaum, are based on RSA.
Anyway, the basic idea is that someone buys a blind signature from the mixer, then some time later uses that signature to get money back, but the mixer can't connect the two. The blind signature is not used to directly sign bitcoin transactions.