Knowledge Base

Cipher Suite

C

TLS_­ECDH_­RSA_­WITH_­AES_­256_­CBC_­SHA384

Summary

Name:
TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
IANA Name:
TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
Code:
(0xc0, 0x2a)
OpenSSL Name:
ECDH-RSA-AES256-SHA384
Protocol Versions:
TLS 1.2

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Components

C
Key Exchange Method
Name

ECDH (Fixed Elliptic-curve Diffie-Hellman)

Security

Static Elliptic-curve Diffie–Hellman[434][435] key exchange is a variant of the Elliptic-curve Diffie–Hellman[114][115] key exchange protocol using elliptic-curve cryptography[118][119][120][121]. It has no forward secrecy[127][128][129][130], and does not protect past sessions against future compromises. If long-term secret keys or passwords are compromised, encrypted communications and sessions recorded in the past can be retrieved and decrypted. Leading client applications do not use this algorithm. Unless your application or requirements specifically call for their use, it is generally safer to avoid cipher suites that are not adopted and supported by a critical mass of the industry.

Recommendations

Remove the cipher suite from the list of cipher suites supported by your server or replace the cipher suite with it's Ephemeral Diffie-Hellman[405][406][407][408] version.

A+
Authentication Method
Name

RSA

Security

Rivest–Shamir–Adleman[275][276][277] is a digital signature[107][108][109][110] algorithm, which is considered secure, however there are known weaknesses[278][279][280][281][282].

A+
Encryption Type
Name

AES-256

Security

Encryption algorithm Advanced Encryption Standard[302][303][304][305][306][307][308][309] is a block cipher[78][79][80][81] for which there is no known practical attack that would allow the attacker to recover the encrypted text without knowledge of the key when the algorithm is implemented correctly. However improper implementations may lead to a side-channel attack[69][70][71] as it has happened in case of OpenSSL[395][396] [310][311][312].

Recommendations

Prefer cipher suites with greater key size of AES (eg: perfer AES-256 over AES-128).

B
Encryption Mode
Name

CBC

Security

Encryption mode is cipher block chaining[28][29][30]. It is vulnerable[31] to timing attack[188] (eg: Lucky Thirteen attack[11][12]) and padding oracle attack[63][64][65][66] (eg: POODLE attack[13][14][15]).

Recommendations

Remove the cipher suite from the list of cipher suites supported by your server or at least set the cipher suite order explicitly and any cipher suite modes be preferred over ciphers suites with CBC modes.

A+
Encryption Key Size
Name

256

Security

The symmetric key[185][186][187] withkey size[184] more than 128 bits as it is should be according to National Institute of Standards and Technology[470][471] so it is not vulnerable to preimage attack[67] and it cannreliably prove that message came from the stated sender (its authenticity) and has not been changed, so connection is not open for a man-in-the-middle attack[61].

Recommendations

Remove the cipher suite from the list of cipher suites supported by your server.

A+
Encryption Block Size
Name

128

Security

The block cipher[78][79][80][81] uses a block size[87] larger than 64 bits, so it is not vulnerable to sweet32 attack[22][23][24][25].

A+
Message Authentication Code
Name

SHA2-384

Security

message authentication code[135][136][137][138] is a hashed message authentication code[139][140][141][142][143][144][145] which is considered secure. The underlaying cryptographic hash function[94][95][96][97] (Secure Hash Algorithm 2[212][213][214]) is also considered secure.

Recommendations

If your application or requirements specifically call for the use of a message authentication code[135][136][137][138] that does not provide authenticated encryption[74] prefer block cipher mode of operation[82][83][84][85][86] (eg: counter with CBC-MAC[32][33][34], Galois/Counter Mode[46][47][48][49] or message authentication code[135][136][137][138] (eg: Poly1305[458][459]) that proved authenticated encryption over the ones which does not provide it. In case of a hashed message authentication code[139][140][141][142][143][144][145] prefer message authentication code[135][136][137][138] based on Secure Hash Algorithm 2[212][213][214] over the ones based on Secure Hash Algorithm 1[202][203][204].