Questions tagged [certificates]

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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4answers
26k 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 ...
34
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3answers
4k views

Does “Shattered” actually show SHA-1-signed certificates are “unsafe”?

Note: I am not advocating anyone continues using SHA1-signed certificates: they are dead as far as security is concerned and should no longer be used. I'm just trying to clarify my understanding of ...
6
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2answers
7k 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 ...
4
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4answers
2k views

Signature and Timestamp for Long Term Document Archival Question

I have a PDF document intended for long-term (many years, maybe decades) archival which I would like to digitally sign with my personal certificate to ensure its integrity. As far as I understand, I ...
3
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2answers
1k 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 ...
1
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1answer
625 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 ...
1
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1answer
5k 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 ...
10
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1answer
5k views

Why does the PKCS1 RSA private key structure contain more than just exponent and modulus?

The ASN.1 spec for the PKCS1 RSA private key format is as follows: ...
5
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4answers
16k 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 just ...
5
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2answers
8k 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 ...
8
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2answers
2k views

Why is a CSR signed and which key is used for signing?

I know that a CSR includes a public key from which a signed certificate shall be generated. But why is the CSR istself signed and which key is typically used? For signing I need a private key, so the ...
8
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2answers
293 views

Must root certificates be self signed?

Root certificates are normally self-signed. What is the reason behind that convention? I mean, one must trust the root certificate in a non cryptographic way anyhow.
7
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1answer
1k views

How is OID 2a 86 48 86 f7 0d parsed as 1.2.840.113549?

I saw that an RSA key, created by OpenSSL, contains the following HEX string: 2a 86 48 86 f7 0d 01 01 01 that HEX string gets interpreted as Object ID: 1.2.840.113549.1.1.1 It is obvious 01 01 ...
5
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2answers
251 views

Can S/MIME be still considered secure?

Previoulsy I had asked this question at https://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 ...
4
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2answers
3k views

Certificate Authority RSA key expiration?

My understanding about SSL/TLS for HTTPS is that servers send their certificates to browsers and browser attempt to decrypt them using trusted CA public keys that are already presented in their store. ...
4
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3answers
543 views

Deduce modulus N from public exponent and encrypted data

This is an RSA question, given data encrypted with a public key from an unknown RSA certificate of 2048 bit, let $X$ be the encrypted data, $M$ the unencrypted data, $c$ the public exponent and $N$ it'...
2
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1answer
367 views

How to identify RSASSA-PSS from rsaEncryption OID?

Following the RFC 8446 it states that: RSASSA-PSS RSAE algorithms: Indicates a signature algorithm using RSASSA-PSS [RFC8017] with mask generation function 1. The digest used in ...
2
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1answer
2k 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 ...
1
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3answers
724 views

How does the certificate trust model work in detail?

How does the whole achitecture between the certificate authority (e.g VeriSign) and its clients (e.g foo.com) work. How does my browser know that foo.com hasn't created its own certificate, wrote "...
1
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2answers
621 views

Why is the signature field in X.509 a BIT STRING, despite there being ASN.1 (DER) data inside?

As can be seen from the following ASN.1 definition of an X.509 certificate, the Signature field is a BIT STRING. ...