A certificate consists of a public key and information about the owner (e. g. the name of a person or server).

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What should I think about these unique certificate serial numbers [closed]

I was looking at the serial numbers of the certificates for www.google.com and wordpress.com. Wordpress was listed by openssl as: 04:0B:D4:F8:25:88:C5 This serial is listed as the serial for both ...
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16 views

How to get the (x,y) from the EC point in the pubkey of an ECDSA certificate?

I have this certificate, and I have the bitstring of the pubkey that should represent Q = (x,y) = [d]P. How can I get the x part? (The curve is the NIST B-163)
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14 views

Protocol for signing and timestamping documents for e-archive system [migrated]

we are building system for storing PDF file for long term in database. Before we store PDF file in database we have to: ...
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1answer
57 views

where should private and public keys be stored? [closed]

I am kind of confused whether should a newly generated key pair be stored in a keystore or in just a normal plain text file? From what I read from online source, there are serveral explainations ...
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1answer
38 views

How are messages from server secured when using SSL certificate

In case of using SSL the certificate server has a primary key and a public key that is published to all clients - as far as I understood. So in this case when message is encrypted by public key (on ...
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2answers
69 views

How does a certificate authority issue a digital certificate?

I am new to cryptography and I want to know the details of how a Certificate Authority issues a digital certificate. From what I know (please correct me if I'm wrong at any parts of my explanation): ...
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1answer
48 views

Why rogued certificate from hash collision is harmful

I cannot understand why rogued certificate is thought harmful though It can be used to impersonate some website. The attacker can craft a rogued certificate with different identities and public key ...
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1answer
45 views

Meaning of Signature hash algorithm field in certificate

I'd like to understand what is the meaning of this field, especially considering that when calling a crypto library to sign data the digest method is specified by the caller. For example, this simple ...
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36 views

Signature constructor using Self-signed certificate

I've the following scenario: One application signs JWT access/id tokens using the private key contained in a self-signed certificate, and then passes its public key to other parties to validate that ...
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46 views

Workaround to implementing Forward Secrecy

In the case where I am self-signing my digital certificates, if I just change my certificate (generate a new one) every week or month, will this have (sort of similar to) the same effect as ...
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71 views

x509 Certificate Signature

I've got a question about the signature of a CA. As I understand, the CA takes the public key of the client and signs it with his own private key by using "md5WithRSAEncryption" (like explained here: ...
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3answers
90 views

Possible to use an accumulator to “license” or restrict the qty of certificates being used?

Suppose in a future version of x509 PKI, it is possible to limit the quantity of certificates being used, what would that look like? Here is a concept that won't work in the real world, but ...
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43 views

Unique assignment of X.509 certificate to each client

I'm trying to implement a short scale electronic voting application in a domain comprised of no more than 100 clients. System administrator is able to create new election instances and each client is ...
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97 views

RSA - Why should we sign hash rather than raw content? [duplicate]

Apart from obvious performance considerations, is there any mathematical or crypto reasons that imply that we sign a hash rather than a raw content ? I read that it was because the hash must fit in ...
2
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2answers
135 views

Smart Card - Entropy during on-board public key generation

I know that some (advanced) smart cards or tokens allow generating key pair directly on the device, but I wonder how the card can gather entropy during the process. Any idea ?
2
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2answers
127 views

how to let other people respond to emails only decrypt-able with my private key

First of all I have to say it's a homework question but since I have no one to consult with, I ended up here :) Suppose a case in which you are the manager of a company and all employees encrypt ...
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36 views

Modifying algebraic secrecy message to use digital certificates

I have the following message: sign((M’, T$_A$, sign((encrypt((encrypt(M, $K_{pbB}$), M’), K), T$_B$), $K_{sB}$)), $K_{sA}$) Sign is used for signature generation. Encrypt is used for ...
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62 views

Generating a public key certificate with ECDSA params

I have an ECDSA key generated in a HSM and I am able to retrieve it's public key components via the PKCS11 library. I would like to create a public x509 certificate with the public params for the ...
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1answer
101 views

EC Public Key length in ASN.1 DER

I have two X.509 certificates in DER format. A: ...
4
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3answers
2k views

Diffie-Hellman and man-in-the-middle attacks

See here for the man-in-the-middle attack on Diffie-Hellman that I'm concerned about: What is Diffie-Hellman? How do we combat this? I have two questions: Is one solution for both Alice and Bob ...
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4answers
10k views

Recommended skills for a job in cryptology [closed]

First let me apologize if this is an ill posed question. Let me also note that I do not in any way seek a comprehensive answer, simply your thoughts on what makes for a valuable asset to a company ...
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200 views

What does “G2” mean when used with X509 certficates and certificate authorities?

For example "Google Internet Authority G2"?. I thought it was another way of specifying Class 2 (for organizations, for which proof of identity is required) but then see certificates such as "VeriSign ...
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3answers
457 views

Are there other digital certificate formats than X.509?

Hi I am a little new to security, but in researching digital certificates it seems the only format people describe is X.509. Are there other formats? If so what are they and where can I find ...
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148 views

RSA and ECDSA Certificate Sizes

Is there a table (or a whitepaper from official sources) that compares the size of X509 certificates generated with RSA (starting from 1024 bits) and ECDSA (starting from 160 bits) ? Thanks for the ...
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1answer
76 views

x509 CA trust question

I'm trying to understand the logic of CAs, trust and client certificates. I have a general understanding but am having a tough time bridging some gaps. In a hypothetical situation a software system ...
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1answer
160 views

Reusing PGP key when generating SSL Certificate Authority?

Does it make sense to reuse some of the keys from my PGP (gnupg, gpg) keyblock when generating my own SSL Certificate Authority (a toy one for myself and a few web services of mine)? In an ideal ...
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1answer
2k views

Diffie-Hellman Key Exchange with Authentication: Man-in-the-Middle query

I have been reading up on MiTM attacks, and the prevention of them using public key certificates. Recently I learnt about Diffie-Hellman Key Exchange with Authentication, and how it uses signed ...
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84 views

Any field in a PKI certificate where some text info can be stored?

I want to store 5-10 lines of Text Info in a PKI Certificate. All I want is that when using common tools like openssl command line or certutil from Microsoft, this text info should be displayed as is. ...
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2answers
505 views

Certificateless cryptography

While reading "Certificateless Public Key Cryptography" by Author Sattam S. Al-Riyami and Kenneth G. Paterson, they have considered generation of private keys by a Key Generation Center (KGC). If the ...
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1answer
265 views

Verification of identity by certification authority

I have question about how a user's identity is verified by a Certification Authority. As I understand it, the process works as follows: User generates his private key and (with the help of private ...
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1answer
248 views

What exactly is inside a private key?

May sound stupid to many, but I would like to have some pointers on what exactly is contained inside a private key. I have decent understanding of public/private keys/certificates (have created them ...
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2answers
114 views

Could someone reuse client certificates?

To my understanding, if a server “cert+key” (RSA) is compromised, than the SSL/TLS network traffic can be decrypted. What about a client “cert+key” (RSA)? Could someone reuse client certificates? ...
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2answers
1k views

What happens when a root CA has its private key compromised?

What happens when a root CA has its private key compromised? Then all children in the tree are compromised too? And then all certificates are compromised? What needs to happen then? Related: - How ...
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1answer
186 views

I've got my private key compromised. How does CRL work?

How does certificate revocation list (CRL) work? How can I send a request to the CA to add my current private key to the CRL, so no one except me can add my certificate to the CRL? Related: - How can ...
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278 views

How can we get CA's public key?

To get a public key of some organization or someone we want to send an encrypted message to, we need to make a request to CA asking that organization's public key. CA then returns X509 certificate. It ...
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1answer
558 views

OpenPGP/X.509 bridge: how to verify public key?

I'd like to use OpenPGP authentication over TLS, but lack of implementations made me use a temporary solution: an OpenPGP/X.509 bridge certificate. The approach is very similar to the approach used ...
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1answer
296 views

Can you explain partial private key extract algorithm in certificateless Public key cryptography?

Related to the algorithms of certificate-less Signature approach of Al-Riyami and Paterson… Why is there a need for a "partial private key extract algorithm"? Why should it be needed when ...
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1answer
75 views

How to pass an arbitrary signature to a certificate

I am trying to sign certificate (X509) using secret sharing. That is shareholders combine their signatures to produce the final signature which will be in this case the signed certificate. However ...
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213 views

How do I sign data that's been encrypted using public key? (RSA)

I've received a public key to encrypt my data for the other end to decrypt using their private key. Now, they want us to sign the data as well to ensure non-repudiation. I thought that I should only ...
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2answers
268 views

How is SSL secure from rogue Certificate Authorities?

There's one thing that I've never quite understood about SSL (which perhaps means I don't understand SSL at all): how is SSL secure from rogue Certificate Authorities? This is probably best ...
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138 views

Certificate == signed public key

For primes p and q used to create a keypair, I understand that the following operation is used to create a signature: $M^d (\bmod\ N)$ where d and N have their usual meanings and M is the message. ...
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Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? [closed]

Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? I know you can, of course, use a 4096 bit key for your server certificate, but I usually see 2048 bit ...
4
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1answer
107 views

What security do digital signatures provide (like used when signing PDFs)?

I want to ask you one question about digital signatures as they are (for example) used when digitally signing PDFs. We know that if our document has a digital signature, we can detect if the original ...
4
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3answers
390 views

Can we design a public-key infrastructure without certificate authorities?

In a recent essay, Bruce Schneier tasks the engineering community with redesigning and rebuilding the vulnerable parts of the Internet's backbone. We need to figure out how to re-engineer the ...
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2answers
179 views

Can S/MIME be still considered secure?

Previoulsy I had asked this question at http://stackoverflow.com/questions/18235983/can-s-mime-be-still-considered-secure but I feel this forum is topic-wise the right place. Recently there has been ...
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1answer
424 views

How does certificate-based encryption solve key revocation problem?

How does certificate-based encryption solve key revocation problem? For example, if a user accidentally reveals its secret key or an attacker compromises it, the user may request revocation of its ...
4
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1answer
467 views

Client and server using same SSL certificate - any issues?

I'm working on software where multiple components will communicate with each other using SSL. There would be one central component acting as a server, which would also require the clients to present ...
2
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1answer
399 views

Generate an insecure public / private key pair

I am looking for a way to generate an "insecure" public key pair. and by insecure I actually mean a pair that is breakable using brute-force (or other encryption) methods. As far as I know PGP ...
2
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216 views

Creating colliding x509 certificates: Crafting RSA moduli step

I am trying to generate 2 x509 certificates with the same signature but different values in the common name field, based on md5 collisions, as it was specified in this paper (page 7). Now I have ...