Re: aes/gcm maximum plaintext size; handling of large files

------=_Part_495060_335179762.1755032832906
Content-Type: multipart/alternative; 
	boundary="----=_Part_495061_969120442.1755032832906"

------=_Part_495061_969120442.1755032832906
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tuesday, August 12, 2025 at 8:10:03=E2=80=AFAM UTC-4 Jeffrey Walton wrot=
e:

GCM plaintext maximum length is specified in bits, not bytes. See=20
SP800-39D, Section 5.2.1.1 Input Data, p. 8, <
https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.p=
df>.=20
That leads to:

    2^39 - 256 =3D 549755813632
    549755813632 / 8 =3D 68719476704


Is there a standard practice for handling AES encryption of large files? =
=20
E.g., create a new IV and resume encryption?  Use something other than GCM=
=20
which has a higher limit?

Thanks!
=20

--=20
You received this message because you are subscribed to the Google Groups "=
Crypto++ Users" group.
To unsubscribe from this group and stop receiving emails from it, send an e=
mail to [email protected].
To view this discussion visit https://groups.google.com/d/msgid/cryptopp-us=
ers/d73104f5-75e6-4bdd-a8ba-63d16704333an%40googlegroups.com.

------=_Part_495061_969120442.1755032832906
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div><div dir=3D"auto">On Tuesday, August 12, 2025 at 8:10:03=E2=80=AFAM UT=
C-4 Jeffrey Walton wrote:<br /></div><blockquote style=3D"margin: 0px 0px 0=
px 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><d=
iv dir=3D"ltr"><div><div>GCM plaintext maximum length is specified in bits,=
 not bytes. See SP800-39D, Section 5.2.1.1 Input Data, p. 8, &lt;<a href=3D=
"https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.=
pdf" target=3D"_blank" rel=3D"nofollow">https://nvlpubs.nist.gov/nistpubs/L=
egacy/SP/nistspecialpublication800-38d.pdf</a>&gt;. That leads to:</div><di=
v><br /></div><div>=C2=A0 =C2=A0 2^39 - 256 =3D=C2=A0<span>549755813632</sp=
an></div><div><span>=C2=A0 =C2=A0 549755813632 / 8 =3D=C2=A0</span><span>68=
719476704</span></div></div></div></blockquote><div><br /></div><div>Is the=
re a standard practice for handling AES encryption of large files?=C2=A0 E.=
g., create a new IV and resume encryption?=C2=A0 Use something other than G=
CM which has a higher limit?</div><div><br /></div><div>Thanks!</div><div>=
=C2=A0</div></div>

<p></p>

-- <br />
You received this message because you are subscribed to the Google Groups &=
quot;Crypto++ Users&quot; group.<br />
To unsubscribe from this group and stop receiving emails from it, send an e=
mail to <a href=3D"mailto:[email protected]">cryp=
[email protected]</a>.<br />
To view this discussion visit <a href=3D"https://groups.google.com/d/msgid/=
cryptopp-users/d73104f5-75e6-4bdd-a8ba-63d16704333an%40googlegroups.com?utm=
_medium=3Demail&utm_source=3Dfooter">https://groups.google.com/d/msgid/cryp=
topp-users/d73104f5-75e6-4bdd-a8ba-63d16704333an%40googlegroups.com</a>.<br=
 />

------=_Part_495061_969120442.1755032832906--

------=_Part_495060_335179762.1755032832906--