The real issue is that most of the Cisco IOS versions use 1024-bit key size for Diffie-Hellman used for key exchange, by default. Though, there are old Cisco IOS versions that use 768-bit DH key size, by default. Prior the year of 2016, 1024-bit key size is adequate. However, NIST’s recommendation is to use 2048-bit key size or higher.

The real issue is that most of the Cisco IOS versions use 1024-bit key size for Diffie-Hellman used for key exchange, by default. Though, there are old Cisco IOS versions that use 768-bit DH key size, by default. Prior the year of 2016, 1024-bit key size is adequate. However, NIST’s recommendation is to use 2048-bit key size or higher. crypto key generate rsa general-keys modulus 2048. But I'm still seeing a 1024 key, anyone know why this is? SSH Enabled - version 2.0 Authentication timeout: 120 secs; Authentication retries: 3. Minimum expected Diffie Hellman key size : 1024 bits. IOS Keys in SECSH format(ssh-rsa, base64 encoded): EDIT: Figured out my problem, needed this no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1 . I've searched and found similar issues here and elsewhere which were solved by increasing the size of the diffie-hellman key used to something like 2048 or 4096 with the cli command `ip ssh dh min size 2048`. Diffie-Hellman key exchange (D–H) is a method that allows two parties to jointly agree on a shared secret using an insecure channel. Exchange Algorithm ¶ For most applications the shared_key should be passed to a key derivation function. Jul 30, 2017 · 3.7. diffie-hellman-group14-sha256. This key exchange uses the group14 (a 2048-bit MODP group) along with a SHA-2 (SHA2-256) hash. This represents the smallest Finite Field Cryptography (FFC) Diffie-Hellman (DH) key exchange method considered to be secure. It is a reasonably simple transition to move from SHA-1 to SHA-2. This method MUST be

## The larger the key size, the better the security, but also the more resources the key processing consumes. The key exchange algorithm. Perfect Forward Secrecy (PFS) ephemeral key exchange algorithms such as Diffie-Hellman Ephemeral (DHE) Elliptic-Curve Diffie-Hellman Exchange (ECDHE) consume more processing resources than Rivest-Shamir-Adleman

Diffie-Hellman key exchange (D–H) is a method that allows two parties to jointly agree on a shared secret using an insecure channel. Exchange Algorithm ¶ For most applications the shared_key should be passed to a key derivation function. Jul 30, 2017 · 3.7. diffie-hellman-group14-sha256. This key exchange uses the group14 (a 2048-bit MODP group) along with a SHA-2 (SHA2-256) hash. This represents the smallest Finite Field Cryptography (FFC) Diffie-Hellman (DH) key exchange method considered to be secure. It is a reasonably simple transition to move from SHA-1 to SHA-2. This method MUST be Does JDK 1.8 support Cipher suites with Diffie-Hellman (DH) keys of size 4096 bits. Ask Question Asked 5 Java 8 Diffie Hellman key size issues with 32 bit linux. 5.

### From the openssl wiki page for the Diffie Hellman Key Exchange: If Alice and Bob wish to communicate with each other, they first agree between them a large prime number p, and a generator (or base) g (where 0 < g < p). Alice chooses a secret integer a (her private key) and then calculates g^a mod p (which is her public key).

It is largely accepted that Diffie-Hellman configured with a key share size of 1024 bits or lower is considered weak and that a nation state would have the resources to be able to break the cipher. To combat this, the TLS server must ensure that Diffie-Hellman enforces key share sizes greater than or equal to 2048 bits. The Finite Field Diffie-Hellman algorithm has roughly the same key strength as RSA for the same key sizes. The work factor for breaking Diffie-Hellman is based on the discrete logarithm problem, which is related to the integer factorization problem on which RSA's strength is based. Thus, a 2048-bit Diffie-Hellman key has about the same strength Executive Summary Microsoft is providing updated support to enable administrators to configure longer Diffie-Hellman ephemeral (DHE) key shares for TLS servers. The updated support allows administrators to increase the size of a DH modulus from the current default of 1024 to either 2048, 3072, or 4096. A security audit I just ran turned up that we are using a sub-par key strength (recommended 2048 or higher, ours is 1024 bits) for the Diffie-Hellman groups (TLS). Upon researching I found that starting JDK 8 we can set the DH key size to be 2048. Diffie-Hellman (DH) keys of sizes less than 1024 bits are deprecated because of their insufficient strength. You can now customize the ephemeral DH key size with the system property jdk.tls.ephemeralDHKeySize. This system property does not impact DH key sizes in ServerKeyExchange messages for exportable cipher Diffie-Hellman key changes Windows 10, version 1507 and Windows Server 2016 add registry configuration options for Diffie-Hellman key sizes. For more information, see KeyExchangeAlgorithm - Diffie-Hellman key sizes .