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Questions tagged [cryptography]

Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for password storage) and digital signatures (provable integrity and authenticity with non-repudiation).

110 questions with no upvoted or accepted answers
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370 views

What is the difference between TEE and HSM in Android Pie?

Android has the concept of hardware backed security as TEE and in latest Android i.e., Android Pie devices can have a HSM (Strongbox). What is the actual difference between TEE and HSM? Does ...
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88 views

How do (broadcast-only/passive) RFID licence plates assert their identity?

I would have guessed by some kind of challenge-response, but there seem to be many claims of 'passive' or 'broadcast-only' tags in the plates. For example from http://www.e-plate.com/security.html: ...
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525 views

How rf remotes for “cloning” rolling code find matching codes?

I've been tinkering with a rf (garage door) remote control that has a scanner mode (google JMA SR-48 for details). This mode works for Mutancode and Erreka which I assume would be similar to KeeLoq. ...
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1answer
338 views

Secret Santa - implementation that does not require a participant to trust the server

In the Christmas spirit I read Cryptographic Secret Santa from MathOverflow, and then followed the link to another page titled Cryptographic Secret Santa. On this latter page the author explains an ...
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138 views

Using asymmetric keys for two factor authentication

Here's what I'm trying to do: Multiple users with different devices will share the same copy of a file which is encrypted on server-side using AES with a randomly generated passphrase, the passphrase ...
3
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91 views

How dangerous is it to transmit the last N bytes of a datagram in plaintext?

I'm developing software for a university satellite project, and am currently working on the communications protocols. Here are the restrictions: Radio packets should be assumed to be no larger than ...
3
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2answers
7k views

Disable support for static key cipher suites

I have a requirement to disable in the windows 7 computers of the company the support for static key cipher suites. I have searched and found that this registry key, holds the allowed cipher suites, ...
3
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2answers
1k views

Can TPM “Storage Keys” be created outside the TPM?

I am interested in 'adding' preexisting keys to a TPM's storage hierarchy. An example of a desired key hierarchy can be shown as: (SRK)----->(User Storage Key)-------> User Working Key 1 ...
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3answers
127 views

Do integrity and authentication always come together?

I cannot come up with a case where there is only one of them. When there is integrity, a random person cannot modify the message without being noticed. That is, an unauthenticated user cannot modify ...
2
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0answers
403 views

Testing a padding oracle vulnerability with PadBuster

I scanned my server with nikto and it shows me that its vulnerable to padding oracle vulnerability + OSVDB-68127: Server is vulnerable to http://www.microsoft.com/technet/security/bulletin/MS10-070....
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420 views

How do I disable TLS Session Tickets in Chrome?

According to ssllabs SSL Session tickets are enabled by default. These are the weakest link in TLS, how do I disable them? I'm using the latest stable.
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92 views

How to make sure your API key cannot just be copied and used

One thing I often struggle with when developing my API's is authentication. I didn't have much trouble with this when I was making them for just a single website and was able to implement the ...
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41 views

Can ECC correctness issues in CVE-2015-2730 allow “remote attackers to spoof ECDSA signatures”?

CVE-2015-2730: Mozilla Network Security Services (NSS) before 3.19.1, as used in Mozilla Firefox before 39.0, Firefox ESR 31.x before 31.8 and 38.x before 38.1, and other products, does not properly ...
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152 views

ASN1 Public Key Signature Verification

I'm interested in handling licenses I distribute with my app with ASN1 and including the Public Key within my application. I've already created the Private/Public Keys, but my confusion is in how the ...
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2k views

OpenVPN cipher mode of operation: CFB vs CFB1 vs CFB8

I'm trying to understand the possible settings for the cipher in OpenVPN and somehow rank them security wise. Right now I'm stuck at differentiating the modes of operation CFB, CFB1 and CFB8. How do ...
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337 views

Attacking Bitcoin's blockchain?

The blockchain is a shared public ledger on which the entire Bitcoin network relies. All confirmed transactions are included in the block chain. Because the integrity and the chronological order of ...
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0answers
794 views

Is it possible to use Bouncy Castle crypto library with PKCS#11 HSMs?

Is it possible to use Bouncy Castle crypto library with PKCS #11 HSMs?
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0answers
95 views

Is this a valid approach for multi-sign?

Requirement: An "arbitrary text" should be encrypted, and keys distributed among 3 people, atleast two keys are needed to unlock. Here is how I plan to do it, please let me know if I'm missing ...
2
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0answers
34 views

Is the crypto-key pair in IPv6 SeND persistent?

IPv6 introduces the NDP extension SeND to help mitigate identity theft, however, is the non-PKI public/private key pair used during the process persistent to some degree, or generated on every ...
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232 views

OpenPGP smartcards compromised by blackhat 2015 simcard hack?

This blackhat was a new sidechannel attack in the SIM-card AES encryption announced. I am currently using the OpenPGP smart/SIM-card version 2.1 to store my PGP-private keys, which is the same model ...
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0answers
113 views

How would an improved “read receipt” work as an email, Facebook post, or webpage?

I'm exploring various ways to implement cryptographic read receipts, that would be used to tell the content producer that the content was viewed. In addition to feedback reporting, a response might ...
2
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0answers
636 views

Which keys does a bank typically exchange with a card scheme?

I'm trying to understand the different EMV-related keys that are shared between a bank who issues EMV cards and a card scheme, such as Visa or MasterCard. I understand the bank would typically ...
2
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0answers
471 views

RSA 4096 key size difference - “sig” and “sig 3”

Whenever I generate a new 4096 RSA key in my GPG program and export the public key to a text file, I get a text file containing a total of around 52 lines (it varies, one of them is 53 lines). ...
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133 views

In U-Prove, what is the purpose of “Pseudonyms”, “Committed”, and “Scope” values and how are they used?

U-Prove allows for anonymous authentication and authorization without the involvement of an IdP. When a client generates a presentation proof 3 values can be optionally included, but I can't find ...
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2answers
63 views

Should I chunk or not for AES-GCM file encryption

New to file encryption. Need to use AES-GCM for file encryption, can't change the alg. Heard about the max plain text size should be 64GB with same key and IV pair. Environment is python 3 with ...
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70 views

Outcome of Needham-Schroeder protocol

I am studying Needham-Schroeder protocol in my course subject and I understood it well, but there is a homework problem which is asking, "what is the outcome of Needham-Schroeder protocol?" ...
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39 views

TDE - Does Key Rotation involve full tablespace Decryption and Re-Encryption?

In Oracle DB 12c, which uses TDE-Tablespace level. If i want to implement key rotation policy, what is the impact? 1. Is it the Tablespace key that will be rotated or the Masterkey? 2. Does key ...
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2answers
76 views

Secure API key mechanism for identification

In my web application, when the user logs in, a pair of JWT(JSON web tokens),access token and refresh token is sent with some fixed time validity. Using access token client is authenticated and using ...
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0answers
83 views

Convert python-pkcs11.types.PrivateKey to PrivateKeyInfo or PrivateKey

I'm building a CertificateListBuilder but it requires the python-pkcs11.types.PrivateKey to be an instance of asn1crypto.keys.PrivateKeyInfo or oscrypto.asymmetric.PrivateKey. How to do it? Is it ...
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0answers
85 views

Does using both a counter and a random nonce make sense for the purpose of reducing the likelihood of replay attacks?

I am aware that using a counter or a random value are both acceptable ways of generating nonces, depending on the circumstances. The tradeoff with using a counter is the necessity to keep state and ...
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0answers
274 views

Digital Signature is not valid

I recently received a digital signed email from a friend and the certificate is issued by COMODO RSA Client Authentication and Secure Email. My problem is the thunderbird detect it as a "Not Valid ...
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1answer
365 views

BitLocker Recovery Key and Microsoft Account Password

I have a Windows 10 Pro machine; the administrator (and only) account is a Microsoft account. I am trying to set up BitLocker to ensure maximum security and safety, even from Microsoft. I understand ...
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0answers
54 views

Identifying and understanding a cryptographic voting protocol

I am reading about a voting protocol using public key encryption. According to the notes, if A votes va, then A broadcasts Ra(Rb(Rc(Ea(Eb(Ec(va)))))). Here, Ra is a random encoding function which ...
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28 views

How large is AppEngine's Private Key?

AppEngine provides methods for signing binary data - e.g. via the Go language's SignBytes[1] However, it doesn't specify any information about how large the private key is. Is this published ...
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303 views

BadPaddingException when using the textbook cipher

I'm using an implementation as below to do an encryption where the bouncycastle is used as the crypto provider. So the ciphertext for a particular plaintext will not be dynamic as the RSA from ...
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0answers
153 views

Why WPA2 did not design a PTK based on asymmetric cryptography?

I was shocked to learn how the PTK is crafted from the PMK in WPA2 WiFi. PMK is made with crypt_hash(SSID + PSK). OK, seems good. Then, the client and the Access Point (AP) make the famous 4 way ...
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70 views

BREACH attack against SPA

I have a single page application that is hosted at example.com that relies on api.example.com. The SPA sends user credentials (JWT token) in authorization header for every request. Let's suppose ...
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0answers
188 views

Android Secure Keystore pre-API 19

Is there any secure Keystore for Android other than Android Keystore? If an attacker used an emulator, saving a key in SharedPreferences or storage is pretty much useless since she'll have direct ...
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0answers
26 views

How server ensures mobile application is running in TEE?

TEE (Trusted execution environment) facilitates secure execution environment for a trusted app. A device can be running both trusted applications and normal applications. How can/ does a server ...
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60 views

Can Hash Length Extension attacks be avoided by changing the data structure?

I read about Hash Length Extension attacks here and here. From the articles I gained that this attack relies on the data structure, in the way that the secret has to be prefixed to the data (please ...
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0answers
586 views

Microsoft CryptoAPI FIPS 140-2

My customer asks me to use FIPS 140-2 validated cryptographic libraries. Currently I have AES 256 encryption using Microsoft CryptoAPI in my application. First I get the provider (HCRYPTPROV) using ...
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0answers
444 views

Are there any DUKPT / AES standards or recommendations?

Are there any standards or industry practices with respect to the implementation of DUKPT with AES (as opposed to DUKPT / TDEA which is covered by ANSI X9.24-1:2009)? Understanding that DUKPT is a ...
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0answers
707 views

How is the Apple FairPlay Server Playback Context (SPC) message generated?

I'm researching encryption tools that use OS-verified hardware such as a TPM or Secure Element. Given that FairPlay only works on iOS and certain Mac hardware, I suspect there is some interaction ...
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0answers
57 views

Secure upload/download design with malicious storage server

Assume we have a malicious storage server (a user-agnostic key-value store, supporting server.put(key, value) and server.get(key)) that we want to use for per-user based secure file storage. The two ...
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0answers
43 views

Why does my email encryption certificate need to be signed?

My email client allows for separate keys for signing and encryption, so my signature key pair can be generated and signed by a third party and my encryption keys can be generated by me personally ...
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0answers
36 views

A query with message block and gray code in LightMAC

In lightMAC the message is divided in to M[1] M[2] and so on eg: M[1]M[2]···M[l] ←− M If we consider AES block cipher 128-bit then I am wondering is the size of individual message block is 128-bit ...
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0answers
331 views

Can RC4 ciphers be disabled in Windows Server 2008?

Having some difficulty with disabling RC4 ciphers in Windows Server 2008 SP2. All the guidance I'm seeing for doing this is specific to Windows Server 2008 R2, including the creation of registry keys ...
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0answers
93 views

OpenSSL API's to pass EC named curve list while generating SSL CTX?

I need to pass the selected EC named curve list to server. Could someone please let me know the OpenSSL API to achieve the same while generating the SSL_CTX?
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137 views

If a HSM RNG is FIPS 140-2 compliant, does that imply FIPS 186-2 compliance also?

If the RNG of an HSM is said to be compliant to FIPS 140-2 (approved DRBG - SP 800-90 CTR mode) does also imply that it is compliant to FIPS 186-2?
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82 views

Substitution Table in TKIP

In TKIP Encapsulation, we divided the per packet key mixing process into two phases. In phase 1, we are taking three inputs i.e temporal key (128-bit session key), transmitter MAC address (48 bits) ...