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Results tagged with aes-gcm
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Deprecated tag, see tag info. Advanced Encryption Standard Galois/Counter Mode, better known as AES-GCM is a mode of operation for symmetric key cryptographic block ciphers that has been widely adopted because of its efficiency and performance. GCM supports authenticated encryption, meaning that the mode not only offers privacy, but also integrity.
1
vote
Accepted
Best practices: AES-GCM parameter (initialization-vector, ...) transport
Are both approaches fine?
Both are fine. The entire point of GCM is that the ciphertext (and nonce and ciphertext) is protected, and so any method of transporting them is fine.
I do want to add …
- 151k
3
votes
Accepted
Can sending the same plaintext twice, each encrypted with different key and IV, weaken the e...
No, it would not compromise the strength of the encryption (assuming that you didn't use a key that the attacker could guess).
We can take it much further; you could give the attacker a billion encry …
- 151k
17
votes
Accepted
Can AES-GCM be broken if initialisation vector is known?
However, we are using the same nonce/IV to encrypt different data.
No, don't do that
if someone indeed gets hold of the plain-text nonce/IV and a number of different encrypted messages (which …
- 151k
4
votes
Accepted
AES-GCM Encryption and Replay Attacks
Is it correct that Alice sends the ciphertext $CT=E_K(IV,AAD,D)$ to Bob together a timestamp $t$ like $CT||t$
That doesn't work; here, GCM doesn't protect $t$; the attacker can easily change it t …
- 151k
6
votes
Accepted
Why is GCM not vulnerable at the birthday bound for 128 bit IV?
Actually, it turns out that GHASH on 128 bit values is a permutation (unless $H=0$; this happens with probability $2^{-128})$
GHASH of a 128 bit value $X$ simplifies to $\text{GHASH}_H(X) = H \times …
- 151k
4
votes
Accepted
How to apply IV and tag to protect messages encrypted using AES-GCM?
1.The IV should be unique for each 128 bit text or for each massage?
Per message. Using an IV of 0 for the first message, 1 for the second, etc is just fine (no matter how long each message is), …
- 151k
3
votes
Accepted
Encryption / Decryption using AES-256 GCM
Exporting the key is sufficient.
With GCM (and block modes in general), the key and the nonce play very different roles.
The key is secret; it is known by the encryptor and the decryptor and no one …
- 151k
1
vote
AES256-GCM padding for unaligned blocks
With SHA256 you pad with 0x80 and then 0x00s, does AES256-GCM require the same?
For GCM, the AAD is zero-padded to a multiple of 16 bytes (with no padding if it's already a multiple of 16 bytes in l …
- 151k
1
vote
Accepted
Performance of AES NI using crypto++
Issue is that the performance is very slow, it is around 2 microseconds, more strangely when I call the function again using same encryptor then it takes only 150 nanoseconds.
Two obvious possibilit …
- 151k
4
votes
Accepted
Why is the subhash key (H) of AES-GCM defined as such?
In GCM, GHASH doesn't use K directly in order to ensure that if GHASH's key is compromised, the master key K remains secret.
Actually, there's not why GCM was designed the way it was (it may be …
- 151k
5
votes
Why this complexity defining AES-GCM counter block?
AES-GCM counter block is defined as nonce || IV || counter
That is not true. AES-GCM effectively has two different versions. If you have a 96 bit nonce, then the counter block is (by your termi …
- 151k
5
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Accepted
Does re-transmission really reduce security?
Your colleague is wrong; assuming that the GCM nonces are generated correctly (that is, never repeats for the same key), there is no risk to GCM in repeating the VCC.
GCM has the property that, as lo …
- 151k
1
vote
Accepted
Does the authentification in GCM serve the same purpose as CRC32?
I do read some article saying, the hacker is able to alter the data which can still result the same CRC computed value in the end.
Obviously, yes. The CRC32 function is completely public, with n …
- 151k
1
vote
What is the use of Additional data or associated data in AESGcm. How it is used while encryp...
Can anybody explain these different fields in both the algorithms and their usage.
Both these fields are designed to detect it if someone in the middle tries to play games with the encrypted data. …
- 151k
5
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AES-GCM: Verification before Decryption
Therefore, the cipher must be decrypted in order to verify its integrity?
No, there is no such requirement. As you state, the authentication tag is calculated from the ciphertext blocks, however, t …
- 151k