Editing Block cipher mode of operation (section)

===={{Anchor|ECB}}Electronic codebook (ECB)====
{{Infobox
|headerstyle  = background:#ccf;
|labelstyle   = background:#ddf;
|header1 = ECB
|data2   = Electronic codebook
|label3  = Encryption parallelizable
|data3   = Yes
|label4  = Decryption parallelizable
|data4   = Yes
|label5  = Random read access
|data5   = Yes
|belowstyle = background:#ddf;
}}
The simplest of the encryption modes is the '''electronic codebook''' (ECB) mode (named after conventional physical [[codebook]]s<ref>{{cite web |title=Recommendation for Block Cipher Modes of Operation |url=http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38a.pdf |website=NIST.gov |publisher=NIST |access-date=1 April 2017 |page=9 |url-status=live |archive-url=https://web.archive.org/web/20170329041940/http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38a.pdf |archive-date=29 March 2017}}</ref>). The message is divided into blocks, and each block is encrypted separately. ECB is not recommended for use in cryptographic protocols: the disadvantage of this method is a lack of [[confusion and diffusion|diffusion]], wherein it fails to hide data patterns when it encrypts identical [[plaintext]] blocks into identical [[ciphertext]] blocks.<ref>{{cite book |last1=Menezes |first1=Alfred J. |url=https://books.google.com/books?id=YyCyDwAAQBAJ |title=Handbook of Applied Cryptography |last2=van Oorschot |first2=Paul C. |last3=Vanstone |first3=Scott A. |date=2018 |publisher=CRC Press |isbn=9780429881329 |page=228}}</ref><ref>{{cite book |last1=Dam |first1=Kenneth W. |url=https://books.google.com/books?id=H8OaAgAAQBAJ |title=Cryptography's Role in Securing the Information Society |last2=Lin |first2=Herbert S. |date=1996 |publisher=National Academies Press |isbn=9780309054751 |page=132}}</ref><ref>{{cite book |last=Schneier |first=Bruce |url=https://books.google.com/books?id=VjC9BgAAQBAJ |title=Applied Cryptography: Protocols, Algorithms and Source Code in C |date=2015 |publisher=John Wiley & Sons |isbn=9781119096726 |page=208}}</ref>



{{multiple image
| header = Electronic Codebook (ECB)
| align = center
| direction = vertical
| image1 = ECB encryption.svg
| caption1 = ECB mode encryption
| image2 = ECB decryption.svg
| caption2 = ECB mode decryption
| width = 512
}}






{{Anchor|ECB-weakness}}
A striking example of the degree to which ECB can leave plaintext data patterns in the ciphertext can be seen when ECB mode is used to encrypt a [[bitmap image]] which contains large areas of uniform color. While the color of each individual [[pixel]] has supposedly been encrypted, the overall image may still be discerned, as the pattern of identically colored pixels in the original remains visible in the encrypted version.

{{multiple image
| align             = center
| image1            = Tux.svg
| caption1          = Original image
| image2            = Tux encrypted ecb.png
| caption2          = Using ECB allows patterns to be easily discerned
| image3            = Tux encrypted ctr.png
| caption3          = Modes other than ECB result in pseudo-randomness
| width             = 196
}}

ECB mode can also make protocols without integrity protection even more susceptible to [[replay attack]]s, since each block gets decrypted in exactly the same way.{{Citation needed|date=April 2020}}