Questions tagged [gcm]

The Galois Counter Mode, an authenticated encryption mode of operation for a block cipher.

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votes
1answer
348 views

Can GCM be used in incremental mode?

I want to sync blobs over the network and the most frequent change will be appending to blob. To minimize data amount sent I would prefer to encrypt appended data, send it over the network, append to ...
2
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1answer
3k views

How to supply the GCM authentication tag to the OpenSSL command line tools?

I'm using AES-256-GCM for authenticated encryption. In order to decrypt, the ruby OpenSSL library requires an auth_tag parameter (in addition to the key and iv). ...
10
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1answer
3k views

Does the GCM authentication tag need to be protected?

I am just learning about the GCM mode of AES and I'd like to start using it in my software. However, I have a question about its use. As I understand it the output of a GCM encryption operation is ...
3
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1answer
925 views

Using same AES-GCM setup for multiple packets?

Most cryptographic libraries I've encountered uses some variant of processPlaintext(...) and then doFinal() to produce the ...
7
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1answer
2k views

Has GMAC mode a future outside GCM?

Once gcm has been implemented for providing both encryption & authentication solution , it appears obvious to consider that such implementation can also provide (if required by new user) a Mac ...
6
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1answer
3k views

Security of authenticated encryption modes GCM & CCM

I have two questions for Clarification for AE mode choice criteria GCM : it appears to be actually the most popular and widely used AE mode of operation. however it is also well-known to be highly ...
12
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1answer
2k views

Windows 8/Server 2012: Passes FIPS-140-2 despite failing AES-GCM for IV != 96 bits long?

Background Microsoft certifies Windows 7/8 as well as Server 2008 R2 and 2012 to be FIPS-140-2 compliant. Actually they certify just a small crypto core, bcrypt.dll (the library, which is unrelated ...
3
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3answers
2k views

RSA digital signature vs authenticated cipher

I want to provide both confidentiality and integrity for data at rest (many large files stored on disk). I plan to encrypt the data using AES, which will cover the confidentiality requirement. So ...
24
votes
1answer
21k views

How to choose between AES-CCM and AES-GCM for storage volume encryption

We are using the encryption built into Solaris 11 ZFS, which offers the choice between CCM (CBC counter mode) and GCM (Galois counter mode). What are the pros and cons of choosing each of these cipher ...
6
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1answer
3k views

How to use GCM mode and associated-data properly

I'm currently migrating a project to use the bouncy castle GCM mode. I understand that using an authenticated mode removes the need for a HMAC, however I want to be sure that I'm using this mode ...
8
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0answers
244 views

Unique GCM/CCM initial counters without recipient side message counters

I am implementing the encryption layer for a communication protocol. The bulk encryption method used is either AES-CCM or AES-GCM. Due to implementation details, encryption of packets is usually, but ...
1
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3answers
877 views

File encryption with one keypair?

I'm working on a program that uses an ECC keypair in a (password protected) PKCS12 file (.pfx) to encrypt files. I like this method because I think it will be higher security (using ECDH to negotiate ...
5
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1answer
1k views

Security for IV in AES-GCM mode

I'd like to use AES-GCM instead of HMAC for authentication and privacy in a token used in a web application, but I'm unsure how to securely tag each token with an IV. Is it safe for me to prepend the ...
14
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3answers
18k views

AES-GCM and its IV/nonce value

I was reading about the differences between the GCM and the CBC more here and I have a follow up doubt on the same. In the CBC mode the person who performs the encryption is the one who provides the ...
3
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4answers
2k views

Which is more secure using a CSPRNG for a One-time pad, or AES?

In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
1
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1answer
6k views

AES GCM symmetric encryption of data at rest in c#, ciphertext much longer than plaintext

I've written encryption/decryption routines using AES GCM. Code can be found here. I recently realized that the cipher text is longer than I believe it should be. It should add the tag and IV onto ...
4
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1answer
6k views

Using “Additional Authenticated Data” as a secondary key

In implementing a cipher in GCM or CCM mode, you are provided the option to add "Additional Authenticated Data" (AAD). This AAD is required for decrypting the cipher text, and seems to be used when ...
6
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1answer
519 views

How to communicate authentication tag for GCM?

I have written some code to do AES in GCM. I currently manually append the tag property to the ciphertext, is this the proper way to communicate the authentication tag?
3
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1answer
3k views

Am I understanding AES GCM implementation correctly?

I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found here for reference. I'll copy in the relevant portions. http://blogs.msdn.com/b/shawnfa/...
71
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1answer
123k views

What is the difference between CBC and GCM mode?

I am trying to learn more about GCM mode and how it differs between CBC. I already know that GCM provides a MAC which is used for message authentication. From what I have read, and from the code ...