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Sep
30
comment Need some understanding on RSA public key exponent
It should be noted that when you generate a RSA key pair, you need to invert $e$ modulo $p-1$ and $q-1$; the natural algorithm for that is the extended GCD (binary GCD is easiest to implement) so you end up computing the GCD anyway.
Sep
26
answered Shared modulus attack on RSA
Sep
15
answered ciphertext packing for bandwidth optimization
Sep
2
awarded  Guru
Aug
23
awarded  Nice Answer
Aug
19
awarded  Nice Answer
Aug
17
awarded  Enlightened
Aug
17
awarded  Nice Answer
Aug
12
comment Can ECDSA signatures be safely made “deterministic”?
Deterministic signatures allow for easier tests of implementations -- you use a known private key, inject a known message to sign, and see if the output is the expected signature. If you do not get to choose or at least know the private key, then deterministic generation is not enforceable.
Aug
12
comment Can ECDSA signatures be safely made “deterministic”?
@Jus12: you cannot verify from the outside whether the signature was done deterministically or not -- except by asking twice for the same signature. If you have a black box that computes signatures, make it sign twice the same data; if you get twice the same output, then chances are that the signature algorithm is deterministic. On a single signature, by design, you should not be able to tell how the internal k value was generated.
Aug
11
awarded  Guru
Jul
27
comment Can you explain Bleichenbacher's CCA attack on PKCS#1 v1.5?
@ddddavidee: thanks; I fixed the link in the answer.
Jul
27
revised Can you explain Bleichenbacher's CCA attack on PKCS#1 v1.5?
Fixed link to Bleichenbacher's article
Jul
26
awarded  Stellar Question
Jul
23
answered Why is Rabin encryption equivalent to factoring?
Jul
16
awarded  Nice Answer
Jul
16
comment Unpredictability of X.509 serial numbers
Integers are integers -- they are not bounded, otherwise we call them modular integers. It so happens that modern computers are most comfortable with integers modulo 32 or 64 bits (i.e. "32-bit or 64-bit integers") but they can still handle larger integers, as they do for RSA. For backward compatibility, X.509 (RFC 5280) says that the serial number shall be positive and its encoded value should fit in 20 bytes, which means that you have 159 bits to play with (serial number shall be between 0 and 2^159-1, inclusive).
Jul
15
awarded  Enlightened
Jul
15
awarded  Nice Answer
Jul
14
answered Is there a multiple asymmetric encryption algorithm, which requires all private keys to reveal the secret?