# Tag Info

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I'll try to give you the big picture and hope it helps you to understand the idea of certificateless public key cryptography (basically, since I do not understand what your question really is about ;) We have three basic approaches in the field of public key cryptography: In traditional public key cryptography, a user $A$ generates a private/public key ...

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In RSA encryption as practiced (that is, to encipher a message which is a short symmetric key), the message size after padding is fixed and equal to the modulus size. Thus the size of the message has no impact on performance. Calculating a modular inverse is performed only during key generation, that is seldom. Also, it has low cost compared to generating ...

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The performance bottleneck with RSA is the modular exponentiation operation. On the other hand, if you are interested in public key encryption performance, perhaps RSA is not the correct tool. RSA is actually fairly fast during its encryption operation; however it is quite slow during the decryption. If you care about decryption performance, you may want ...

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The issue is that we use modular arithmetic. In modular arithmetic, you may view $m \bmod n$ as the remainder of $m$ when divided by $n$. So, for example, $7 \bmod 2 = 1$, also written as $7 \equiv 1 \pmod 2$, because $2(3) + 1 = 7$. Now consider what you're guaranteed by $m \equiv c^d \pmod n$, the decryption formula for plain RSA. You're guaranteed that ...

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A lot of sleepless nights for the CA, their customers, web browser and OS developers, and Slashdot users, that's what. I don't know if a CA has ever had their private keys compromised, but there have been incidents where their systems were broken into and fraudulent certificates were issued. (There's a difference between a private key actually being taken, ...

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That's correct. If this happens, then your PKI is doomed and you have to set it up again and roll out all the certificates again. Actually, then not all the certificates are "compromised" in the sense of key compromise, but you cannot longer trust them, since if someone is in possession of the root private key, this person can issue arbitratrily dated ...

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ECB, CBC and such cipher modes are something that relate to symmetric cryptography. In context of RSA, it is important to study from documentation of the product what they mean as they do not ordinarily apply. Based on the articles you provide, this statement is correct: The mode, ECB in this case, is ignored for RSA.Use PKCSPadding. The max amount of ...

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McEliece NTRU Multivariate If you mean "syntactically public key" instead of "implies the existence of secure key agreement", then there is also hash-based signatures.

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That depends on the concrete CRL. As long as you have access to your private key, you can sign the revocation request. This prevents anyone without access to the private key from issuing a faked revocation request. With access to the private key, a faked revocation request can be sent. But in this case the damage is already done, and a revocation is ...

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Is there any chance of finding symmetric key from encrypted public key? The answer is no, assuming the symmetric key has sufficient entropy and a secure encryption algorithm and mode is used correctly. Modern ciphers like AES with proper secret keys are not vulnerable to known plaintext attacks. Why? This has been answered in an earlier question: Why ...

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Well, ECC takes about $2^{n/2}$ time to break because there are smarter ways to attack it than literally trying each possible key separately. With AES, the best known-attack is to try a key, and see if it works. If it doesn't, all you've learned is that that specific key wasn't it, only $2^{n}-1$ more to go... However, with ECC, there are other methods. ...

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Ok, I sum it up. In ECIES, which is a hybrid encryption scheme, the ciphertext size is one point of the curve + the size of the encrypted message (size of the message + small overhead of padding for the symmetric cipher) + the tag length of the used MAC. As CodesInChaos pointed out, if you work on a 256 bit curve (giving 128 bit security), then using point ...

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No, exposing such a hash does not compromise the RSA private key, unless the hash function is sufficiently and severely broken. Of course, you don't need to hash the private exponent to identify the key. You can simply use the modulus or a hash over the (public) modulus to identify the key. This has the additional advantage that that ID will also match the ...

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For the most common public key encryption mechanisms such as RSA PKCS#1 encryption mechanism, it is indeed possible to deduce the key length from encrypted length. In addition to encrypted length, you may want to look at encrypted data. In case of RSA observing encrypted data will reveal e.g. modulus, i.e. basically the public key. This is generally the ...

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You can search for root certificates of a given CA. E.g.: http://www.symantec.com/page.jsp?id=roots, but this page is served over plain HTTP so maybe you shouldn't trust it! or https://www.mozilla.org/projects/security/certs/included/. From there when you want to check a certificate you can check whether it belongs to/was signed by a root CA you trust. ...

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First of all, as already mentioned in the comments, there is absolutely no mathematics or cryptography involved. Independent of the model used, i.e., public key cryptography, identity based cryptography, or certificateless public key cryptography (as i summed up in my answer here), the identity verification must be established by other means. In the wild ...

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