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Can we use this formula to find GCM data integrity? No. … Is there a similar document for GCM mode? "Breaking and Repairing GCM Security Proofs" by Iwata, Ohashi and Minematsu (2012) has the current security proof for GCM. …

Does Camellia-GCM use Camellia-CTR to create GCM Hash? GCM is a mode of operation for a 128-bit blocksize block cipher that turns it into an authenticated encryption scheme. … So yes, Camellia-GCM uses Camellia-CTR internally in exactly the same way AES-GCM uses AES-CTR internally. with Camellia getting the exact same inputs as AES. …

Internally GCM really is CTR mode along with a polynomial hashing function applied on the ciphertext. …

FIRST: this is a severe abuse of the GCM construction and should be avoided if anyhow possible, use any of the other AES-finalists if you don't trust AES and there's no reason at the moment to do so. … Even more you'd need to write your own GCM-implementation or modify an existing one which may be avoided if possible. …

Yes, you can jump to some random byte in a AES-GCM cipher text and decrypt it, by just applying the underlying CTR decryption, i.e. by incrementing the counter appropriately. …

You really want to give 96-bit IVs to GCM (pad them if neccessary). If you pick any IV size but 96-bit, GCM's polynomial hashing function GHASH is invoked to get the IV size down to 128-bit. … This means that you basically apply a PRF on your IV, which means that there's a decent chance of hitting a collision if you use about $2^{64}$ IVs which will allow for a key-recovery attack on GCM and …

If the counter mode started at $\text{Nonce}\mathbin\|0^{32}$ instead of at $\text{Nonce}\mathbin\|0^{31}\mathbin\|1$ then one could submit an encryption query for $(0^{96},0^{128})$, i.e. the 128-bit …

To answer your ideas of: "I use hash-then-encrypt" with CBC + SHA-1 "I use MAC-then-encrypt" with CBC + HMAC "I won't use GCM because of unclear usage guidance" First, hash-then-encrypt is a really … Third : GCM. You indeed only should encrypt than less than 60GiB of data under a given key-nonce pair. …

As documented in NIST SP800-38D, GCM works as follows, upon input of block cipher $E$, key $K$, initialization vector $IV$, and plaintext $P$: Compute the GHASH key $H=E_K(0^{128})$ Compute the initial … This issue is avoided in "legal" versions of GCM by hashing in the length of the IV for variable-length IVs and for fixed-length IVs by setting the last bit to 1. …

No, there is no black-box type way of increasing the security strength of the tags of CCM and GCM. … However this would most-likely be a GCM look-a-like, but would needs its own (difficult) security analysis and new implementations. On a final note, the tags of CCM, GCM and HMAC are MACs. …

AES GCM is authenticate then encrypt algorithm? because I feel that encrypt then authenticate feels more secure to me AES-GCM is an authenticated encryption algorithm. … and so AES-GCM achieves the same security definition as CBC-then-HMAC. …

Actually section 6.2.3.3 of RFC 5246 talks about the associated data: The additional authenticated data, which we denote as additional_data, is defined as follows: additional_data = seq_num + TLSComp …