Weak Cipher Suite

IANA name:

TLS_RSA_WITH_AES_256_CBC_SHA

OpenSSL name:

AES256-SHA

GnuTLS name:

TLS_RSA_AES_256_CBC_SHA1

Hex code:

0x00, 0x35

TLS Version(s):

TLS1.0, TLS1.1, TLS1.2, TLS1.3

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Protocol:

Transport Layer Security (TLS)

Key Exchange:

Rivest Shamir Adleman algorithm (RSA)

Non-ephemeral Key Exchange:

This key exchange algorithm does not support Perfect Forward Secrecy (PFS) which is recommended, so attackers cannot decrypt the complete communication stream.

Authentication:

Rivest Shamir Adleman algorithm (RSA)

RSA Authentication:

There are reports that servers using the RSA authentication algorithm with keys longer than 3072-bit may experience heavy performance issues leading to connection timeouts and even service unavailability if many clients open simultaneous connections.

Encryption:

Advanced Encryption Standard with 256bit key in Cipher Block Chaining mode (AES 256 CBC)

Cipher Block Chaining:

In 2013, researchers demonstrated a timing attack against several TLS implementations using the CBC encryption algorithm (see isg.rhul.ac.uk). Additionally, the CBC mode is vulnerable to plain-text attacks in TLS 1.0, SSL 3.0 and lower. A fix has been introduced with TLS 1.2 in form of the GCM mode which is not vulnerable to the BEAST attack. GCM should be preferred over CBC.

Hash:

HMAC Secure Hash Algorithm 1 (SHA)

Secure Hash Algorithm 1:

The Secure Hash Algorithm 1 has been proven to be insecure as of 2017 (see shattered.io).

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Included in RFC:

• RFC 5246

Machine-readable:

application/json