Knowledge Base

F

Cipher Suite: TLS_­RSA_­PSK_­WITH_­NULL_­SHA

Summary

Name:
TLS_RSA_PSK_WITH_NULL_SHA
IANA Name:
TLS_RSA_PSK_WITH_NULL_SHA
Code:
(0x00, 0x2e)
OpenSSL Name:
RSA-PSK-NULL-SHA
Protocol Versions:
TLS 1.0,TLS 1.1,TLS 1.2

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Components

C
Key Exchange Method
Name
RSA (Rivest-Shamir-Adleman)
Security
RSA[443][444] key exchange is a key exchange[133] that 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. Throughout its history RSA encryption has had many security flaws[445][446][447][448][449][450] and was affected by variety of attack types: chosen-ciphertext attack[55] (eg: Bleichenbacher's attack[1][2], ROBOT attack[18][19][20][21]), side-channel attack[69][70][71] (eg: padding oracle attack[63][64][65][66], like Bleichenbacher's cat[3][4][5][6]).
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].
C
Authentication Method
Name
PSK
Security
The pre-shared key[160] can ensure authenticity[75][76][77] of the communicating parties mutually based on symmetric key[185][186][187]s that are shared in advance among the parties. Combined with a key exchange[133] that has forward secrecy[127][128][129][130] property algorithm can protect against dictionary attack[58][59]s by passive eavesdroppers (but not active attackers). Pre-shared keys with low entropy[126], may caused by a weakness[171][172][173] of random number generator[168][169][170], can be easily broken in brute-force attack[54]. 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
If your application or requirements specifically call for the use of algorithms which are not used by the leading client applications set the cipher suite order explicitly and cipher suites used by the leading client applications be preferred over the ones which do not used by them.
F
Encryption Type
Name
NULL
Security
Encryption algorithm is a null encryption[360][361] that cannot provide confidentiality[91][92][93], so connection is available or disclosed to unauthorized individuals, entities, or processes.
Recommendations
Remove the cipher suite from the list of cipher suites supported by your server.
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].