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Dec
31
answered Is bcrypt better than scrypt
Dec
31
revised Future proof encryption possible in theory?
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Dec
31
comment Future proof encryption possible in theory?
@drjimbob - I would tend to agree with Graham Hill here; you must always keep the key secret, whether it's a OTP or AES, and so all the "non-computational cryptanalysis" methods you mention will get you an AES key just as easily as a OTP. Therefore the crux of your argument is that for sufficiently long message sizes, OTP storage becomes difficult compared to just 256 bits of an AES key. While I see that point, I think the bigger concern is storing the key and the ciphertext in a manner that will still be accessible in 100 years, after USB, Firewire and SATA have all become extinct.
Dec
30
revised How can I explain the concept of public and private keys without technical jargon?
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Dec
27
answered How to evaluate the strength of a hashing algorithm?
Dec
27
comment How big is the risk of hash fixed points/cycles?
As a succinct answer-as-comment, if a hash algorithm is demonstrated to have this property, called "sticky-state", it is understood to be insecure. KDFs are built on top of secure hashes that have no known cyclical states, and are rigorously tested both theoretically and empirically to ensure that the derivation process itself does not produce cyclical state.
Dec
27
comment X.509 certificate attack (small sha1 private key)
Both the exponent and the modulus form the public key. 65537 is a common exponent value because it is relatively small (but not too small) and it's truly prime, meaning by definition it will be coprime to any modulus. Your equation's wrong; c = m^e mod n. There is then a second exponent d, which is unique for a given modulus and exponent, where m = c^d mod n. d is usually very large, as it must be an integer satisfying the equation d*e mod n = 1. Most implementations don't bother; they use p and q and some clever math to get the same result.
Dec
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awarded  Nice Answer
Dec
22
revised Future proof encryption possible in theory?
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Dec
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revised Future proof encryption possible in theory?
added 167 characters in body
Dec
22
revised Future proof encryption possible in theory?
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Dec
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revised Future proof encryption possible in theory?
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Dec
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comment Future proof encryption possible in theory?
... But not with the same key lengths or padding schemes that we used in the 70s. It isn't just the conceptual algorithm, but the specific implementation, that must stand the test of time.
Dec
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revised Future proof encryption possible in theory?
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Dec
21
answered Future proof encryption possible in theory?
Dec
21
comment X.509 certificate attack (small sha1 private key)
In the example you showed, the modulus and exponent of the public key for the certificate itself are clearly labelled under "RSA Public Key:" as "Modulus" (very large string of bytes) and "Exponent" (65537).
Dec
21
comment Is the date that a password was last changed useful to an attacker?
True all; this is the kind of thing I wanted to tease out. If the account were still vulnerable given the same vectors with or without the data in question, then that data isn't "sensitive". But, it remains to be demonstrated that this information would provide no significant advantage in any situation where it could be accessed.
Dec
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revised Is there an asymmetric encryption algorithm that maintains the length of the plaintext?
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Dec
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revised Is the date that a password was last changed useful to an attacker?
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Dec
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comment X.509 certificate attack (small sha1 private key)
The modulus, N, is the majority of the "public key" (the exponent used for encryption with the public key is typically small). N is a number that is the product of two large prime numbers. Encryption is performed by turning the message into an integer number less than N, raising that message integer to the power of the exponent, then modulo dividing by N. The resulting number is the ciphertext. The ciphertext is decrypted by raising it to a different exponent, but then dividing by the same modulus to obtain the plaintext. See en.wikipedia.org/wiki/RSA_(algorithm)