# Tag Info

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Forward security (a protocol level feature) and key exchange schemes are indeed two orthogonal topics. Forward security says the break of a current key does not allow the attacker to learn any communication in the past. To this end, any protocol that uses ephemeral key exchange scheme (i.e., use new keys for new sessions) is forward secure. The only ...

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I see three main reasons why PAKEs are not widely used yet: The lack of IETF standards. SRP has limitations discussed in the link @fgrieu posted above. Many PAKE protocols have been designed, but they lack a convincing security proof, or properties some applications may expect. This is being solved as we speak. The CFRG is currently having a selection ...

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Assuming that in the question "with public key" describes encryption under the intended recipient's public key; secrecy of the corresponding private keys; that by some external mechanism public keys are securely bound to the legitimate parties; the parties have some unstated convention to define which is Party 1, defining who transmits first and order in "...

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There is no magic solution. Either both parties are in a direct contact to exchange a PSK, or they use authentication based on PKI. Otherwise there is no guarantee that there is no man in the middle.

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1. Authentication then node 2 would know what the clients IP is This statement is not necessarily true. If a certificate is given to a web site, then yes, IP or domain name will be known. But if your client is a person, then certificate can create some email address that can be without any meaning to the world. 2. Pre-shared secret Use a pre-shared ...

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TLS_DHE_RSA_WITH_AES_256_CBC_SHA is 256-bit AES encryption SHA-1 message authentication Ephemeral Diffie-Hellman key exchange Signed with an RSA certificate We can find the answer in rfc5246 Key IV Block Cipher Type Material Size Size ------------ ------ -------- ---- ----- NULL Stream 0 0 ...

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A short a intuitive answer would be that; Perfect forward secrecy would be a cryptographic mechanism where by; If I stole the current private keys a group is using for securing their communications, I would only be able to decrypt the current cipher text. I would however fail to decrypt past & future cipher texts This is because the ...

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If you are doing an ECDH key agreement $[a]B = [b]A = [ab]G$, you should be hashing the ECDH shared secret to derive a key $k = H([ab]G)$ anyway instead of using $[ab]G$ directly, for various reasons. More than that, you should hash the transcript of the key agreement in too, giving $k = H([ab]G, A, B, \mathit{etc.})$. Here $H$ might be SHA-256 or HKDF-...

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$\text{B}_\text{private}$ is $\text{b}$ and $\text{B}_\text{public}$ is $\text{g}^\text{b} \bmod p$. So $\text{B}$ can compute $(\text{A}_\text{public})^b \bmod p = \text{g}^{\text{ab}} \bmod p$

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The gist of it is, Alice is sharing a password with Bob over walkie-talkie with terrible static. Sometimes Bob has to ask Alice to repeat the last character. But Alice will never comply with Eve's requests for repeats. So Bob gets to learn the entire password while Eve does not. This is because occasionally Eve will be unsure of the last character, ...

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