Hello there,
Code:
uname -a
Linux abhi 4.12.0-kali2-amd64 #1 SMP Debian 4.12.12-2kali1 (2017-09-13) x86_64 GNU/Linux
I was updating my repository and got the error. Till yesterday it was running fine. I don't know what is the reason.

i have following repositories in sources.list:
Code:
deb https://http.kali.org/kali kali-rolling main non-free contrib
deb-src https://http.kali.org/kali kali-rolling main non-free contrib
My error was:
Code:
apt-get update

Get:3 https://kali.mirror.garr.it/mirrors/kali kali-rolling InRelease [30.5 kB]  
Get:5 https://kali.mirror.garr.it/mirrors/kali kali-rolling/contrib Sources [67.2 kB]
Get:6 https://kali.mirror.garr.it/mirrors/kali kali-rolling/non-free Sources [122 kB]
Get:7 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main Sources [11.5 MB]
Get:8 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main amd64 Packages [15.4 MB]
Get:9 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Packages [15.4 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Get:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb) [32.0 MB]
Err:10 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main i386 Contents (deb)
  File has unexpected size (31951658 != 31951611). Mirror sync in progress? [IP: 90.147.164.69 443]
  Hashes of expected file:
   - Filesize:31951611 [weak]
   - SHA256:f175f81fc83b623db0671e37f2615f60490f0d2f95f59c2df295451a5d0c9364
   - SHA1:955783b1344915d556a3c103e0c73c209d87c66a [weak]
   - MD5Sum:98b70c8d93103c3a9d2847110ccaad05 [weak]
  Release file created at: Sat, 21 Oct 2017 12:12:36 +0000
Get:19 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main amd64 Contents (deb) [32.1 MB]
Err:19 https://kali.mirror.garr.it/mirrors/kali kali-rolling/main amd64 Contents (deb)
  
Fetched 30.5 kB in 4s (7,328 B/s)     
Reading package lists... Done
E: Failed to fetch https://kali.mirror.garr.it/mirrors/kali/dists/kali-rolling/main/Contents-i386.gz  File has unexpected size (31951658 != 31951611). Mirror sync in progress? [IP: 90.147.164.69 443]
   Hashes of expected file:
    - Filesize:31951611 [weak]
    - SHA256:f175f81fc83b623db0671e37f2615f60490f0d2f95f59c2df295451a5d0c9364
    - SHA1:955783b1344915d556a3c103e0c73c209d87c66a [weak]
    - MD5Sum:98b70c8d93103c3a9d2847110ccaad05 [weak]
   Release file created at: Sat, 21 Oct 2017 12:12:36 +0000
E: Failed to fetch https://kali.mirror.garr.it/mirrors/kali/dists/kali-rolling/main/Contents-amd64.gz  
E: Some index files failed to download. They have been ignored, or old ones used instead.

If i replace them with the http support repository than it works fine i.e
Code:
deb http://http.kali.org/kali kali-rolling main contrib non-free
deb-src http://http.kali.org/kali kali-rolling main contrib non-free
However if i comment out the first one than it doesn't through any error.
Code:
#deb https://http.kali.org/kali kali-rolling main non-free contrib
deb-src https://http.kali.org/kali kali-rolling main non-free contrib


Any suggestion?
Thanks