B

Name:

TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA

IANA Name:

TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA

Code:

(0xc0, 0x0a)

OpenSSL Name:

ECDHE-ECDSA-AES256-SHA

Protocol Versions:

TLS 1.0,TLS 1.1,TLS 1.2

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A+

Key Exchange Method

Name

ECDHE (Elliptic-curve Diffie-Hellman Ephemeral)

Security

Ephemeral Elliptic-curve Diffie–Hellman^{[432]}^{[433]} is a variant of Elliptic-curve Diffie–Hellman^{[114]}^{[115]} key exchange that has forward secrecy^{[127]}^{[128]}^{[129]}^{[130]}, and does protect past sessions against future compromises. If long-term secret keys or passwords are compromised, encrypted communications and sessions recorded in the past cannot be retrieved and decrypted.

Recommendations

Always prefer cipher suites with PFS property over the non-PFS ones. Note that performance considerations implies preferring Ephemeral Elliptic-curve Diffie–Hellman^{[432]}^{[433]} over Ephemeral Diffie-Hellman^{[405]}^{[406]}^{[407]}^{[408]}.

A+

Authentication Method

Name

ECDSA

Security

Elliptic Curve Digital Signature Algorithm^{[266]}^{[267]}^{[268]}^{[269]} is the elliptic-curve cryptography^{[118]}^{[119]}^{[120]}^{[121]} based variant of the digital signature^{[107]}^{[108]}^{[109]}^{[110]} names Digital Signature Algorithm^{[258]}^{[259]}^{[260]}^{[261]}^{[262]}^{[263]} algorithm. It is considered secure ^{[270]}^{[271]} and gives better performance and smaller key sizes.

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

SHA-1

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^{[462]}, despite the fact that the underlayingcryptographic hash function^{[94]}^{[95]}^{[96]}^{[97]} (Secure Hash Algorithm 1^{[202]}^{[203]}^{[204]}) is considered insecure^{[205]}^{[206]}^{[207]}^{[208]}^{[209]}^{[210]}^{[211]}.

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]}.