# Openssl aes-\*-cbc is broken

**URL:** <https://www.ruby-forum.com/t/openssl-aes-cbc-is-broken/59313>\
**Category:** Development\
**Created:** [May 3, 2006, 6:56pm UTC](https://www.ruby-forum.com/t/openssl-aes-cbc-is-broken/59313 "2006-05-03T18:56:50Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![NARUSES\_Yui](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/258eb7/32.png) [@NARUSES\_Yui](https://www.ruby-forum.com/u/NARUSES_Yui)\
**Post date:** [May 3, 2006, 6:56pm UTC](https://www.ruby-forum.com/t/openssl-aes-cbc-is-broken/59313/1 "2006-05-03T18:56:50Z")

</div>

e$B@.@%$G$9!#e(B

openssl e$B%b%8%e!\<%k$Ne(B AES (CBC mode) e$B$,;H$($J$$$h$&$G$9!#e(B

require’openssl’  
c1 = OpenSSL::Cipher::Cipher.new(“AES-256-CBC”)  
c2 = OpenSSL::Cipher::Cipher.new(“AES-256-CBC”)  
pass = “open sesame!”  
data = “Hello world!”  
c1.pkcs5\_keyivgen(pass)  
s1 = c1.encrypt.update(data) + c1.final  
c2.pkcs5\_keyivgen(pass)  
s2 = c2.decrypt.update(s1) + c2.final  
p(data == s2) #=\> true

e$B$r\<B9T$7$h$&$H$9$k$H!"e(Bc2.final e$B$G0J2\<$N%(%i!\<$,H/@8$7$^$9!#e(B  
OpenSSL::CipherError: bad decrypt  
from (irb):359:in `OpenSSL::Cipher::Cipher#final' from (irb):359:in`Kernel#binding’  
from :0

aes-128-cfb aes-128-ecb aes-128-ofb e$B$H$$$C$?e(B  
CBC e$B0J30$N%b!\<%I$G$OF0:n$7$^$9$7!"e(B  
AESe$B0J30$NJ}\<0$Ne(B CBC e$B$OF0:n$7$^$9!#e(B  
e$B$^$?!"e(Bopenssl e$B%3%^%s%I$+$i$@$HF0:n$9$k$N$G!“e(B  
Ruby/OpenSSL  
e$B$NLdBj$@$H;W$&$N$G$9$,!”$=$l0J\>e$OD4$Y@Z$l$^$;$s$G$7$?!#e(B

e$B$H$3$m$G!"e(BOpenSSL::Cipher::AESe$B$G$9$,!"e(B  
openssl e$B$G$Oe(B -aes e$B$,L5$$$?$a!"e(B  
OpenSSL::Cipher::AES.new(256, ‘cbc’)  
e$B$J$I$H$7$J$$$H=i4|2=$G$-$^$;$s!#e(B

OpenSSL::Cipher::AES128, OpenSSL::Cipher::AES192,  
OpenSSL::Cipher::AES256 e$B$J$i$P!"e(B  
e$B$=$l$\>$le(B -aes128, -aes192, -aes256 e$B$HBP1~$9$k$?$a!"e(B  
e$B0z?t$J$7$G%$%s%9%?%s%9$r:n$l$k$N$G$$$$$H;W$&$N$G$9$,!#e(B

---

<div class="post-metadata">

**Author:** ![NARUSES\_Yui](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/258eb7/32.png) [@NARUSES\_Yui](https://www.ruby-forum.com/u/NARUSES_Yui)\
**Post date:** [May 5, 2006, 10:16am UTC](https://www.ruby-forum.com/t/openssl-aes-cbc-is-broken/59313/2 "2006-05-05T10:16:44Z")

</div>

In message [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid),  
`“NARUSE, Yui” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)’ wrote:

> openssl e$B%b%8%e!\<%k$Ne(B AES (CBC mode) e$B$,;H$($J$$$h$&$G$9!#e(B

e$B;n$7$F$\_$k$He(BECBe$B$bF1MM$G$7$?!#e(B

> aes-128-cfb aes-128-ecb aes-128-ofb e$B$H$$$C$?e(B  
> CBC e$B0J30$N%b!\<%I$G$OF0:n$7$^$9$7!"e(B  
> AESe$B0J30$NJ}\<0$Ne(B CBC e$B$OF0:n$7$^$9!#e(B  
> e$B$^$?!"e(Bopenssl e$B%3%^%s%I$+$i$@$HF0:n$9$k$N$G!“e(B  
> Ruby/OpenSSL e$B$NLdBj$@$H;W$&$N$G$9$,!”$=$l0J\>e$OD4$Y@Z$l$^$;$s$G$7$?!#e(B

e$B$J$s$G$=$&$J$k$+$O$A$c$s$HD4$Y$F$J$$$N$G$9$,!"80$He(BIVe$B$r%;%C%He(B  
e$B$9$kA0$Ke(Bencrypte$B$r8F$V$HF0$/$h$&$G$9!#e(B

% ruby -e ’  
require “openssl”  
pass = “open sesame!”  
data = “Hello world!”

c1 = OpenSSL::Cipher::Cipher.new(“AES-256-CBC”)  
c1.encrypt  
c1.pkcs5\_keyivgen(pass)  
s1 = c1.update(data) + c1.final

c2 = OpenSSL::Cipher::Cipher.new(“AES-256-CBC”)  
c2.decrypt  
c2.pkcs5\_keyivgen(pass)  
s2 = c2.update(s1) + c2.final  
p(data == s2) #=\> true  
’

> OpenSSL::Cipher::AES128, OpenSSL::Cipher::AES192,  
> OpenSSL::Cipher::AES256 e$B$J$i$P!"e(B  
> e$B$=$l$\>$le(B -aes128, -aes192, -aes256 e$B$HBP1~$9$k$?$a!"e(B  
> e$B0z?t$J$7$G%$%s%9%?%s%9$r:n$l$k$N$G$$$$$H;W$&$N$G$9$,!#e(B

e$B$=$&$G$9$M!#$3$N5!2q$KDI2C$7$h$&$H;W$$$^$9!#e(B