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Understanding FIPS Mode of Operation Terminology and Supported Cryptographic Algorithms

Use the definitions of FIPS terms and supported algorithms to help you understand Junos OS in FIPS mode of operation.

FIPS Terminology

Critical security parameter (CSP)

Security-related information—for example, secret and private cryptographic keys and authentication data such as passwords and personal identification numbers (PINs)—whose disclosure or modification can compromise the security of a cryptographic module or the information it protects.

Cryptographic module

The set of hardware, software, and firmware that implements approved security functions (including cryptographic algorithms and key generation) and is contained within the cryptographic boundary. SRX Series devices are certified at FIPS 140-2 Level 2.

Cryptographic Officer

Person with appropriate permissions who is responsible for securely enabling, configuring, monitoring, and maintaining Junos OS in FIPS mode of operation on a device. For details, see Understanding Roles and Services for Junos OS in FIPS Mode of Operation.


Encapsulating Security Payload (ESP) protocol. The part of the IPsec protocol that guarantees the confidentiality of packets through encryption. The protocol ensures that if an ESP packet is successfully decrypted, and no other party knows the secret key the peers share, the packet was not wiretapped in transit.


Federal Information Processing Standards. FIPS 140-2 specifies requirements for security and cryptographic modules. Junos OS in FIPS mode of operation complies with FIPS 140-2 Level 2..


The Internet Key Exchange (IKE) is part of IPsec and provides ways to securely negotiate the shared private keys that the authentication header (AH) and ESP portions of IPsec need to function properly. IKE employs Diffie-Hellman key-exchange methods and is optional in IPsec. (The shared keys can be entered manually at the endpoints.)


The IP Security (IPsec) protocol. A standard way to add security to Internet communications. An IPsec security association (SA) establishes secure communication with another FIPS cryptographic module by means of mutual authentication and encryption.


Known answer tests. System self-tests that validate the output of cryptographic algorithms approved for FIPS and test the integrity of some Junos OS modules. For details, see Understanding FIPS Self-Tests.


Security association (SA). A connection between hosts that allows them to communicate securely by defining, for example, how they exchange private keys. As Cryptographic Officer, you must manually configure an internal SA on devices running Junos OS in FIPS mode of operation. All values, including the keys, must be statically specified in the configuration.


Security parameter index (SPI). A numeric identifier used with the destination address and security protocol in IPsec to identify an SA. Because you manually configure the SA for Junos OS in FIPS mode of operation, the SPI must be entered as a parameter rather than derived randomly.


A protocol that uses strong authentication and encryption for remote access across a nonsecure network. SSH provides remote login, remote program execution, file copy, and other functions. It is intended as a secure replacement for rlogin, rsh, and rcp in a UNIX environment. To secure the information sent over administrative connections, use SSHv2 for CLI configuration. In Junos OS, SSHv2 is enabled by default, and SSHv1, which is not considered secure, is disabled.


Erasure of all CSPs and other user-created data on a device before its operation as a FIPS cryptographic module—or in preparation for repurposing the device for non-FIPS operation. The Cryptographic Officer can zeroize the system with a CLI operational command. For details, see Understanding Zeroization to Clear System Data for FIPS Mode of Operation.

Supported Cryptographic Algorithms

Each implementation of an algorithm is checked by a series of known answer test (KAT) self-tests. Any self-test failure results in a FIPS error state.

The following cryptographic algorithms are supported in FIPS mode of operation. Symmetric methods use the same key for encryption and decryption, while asymmetric methods (preferred) use different keys for encryption and decryption.


The Advanced Encryption Standard (AES), defined in FIPS PUB 197. The AES algorithm uses keys of 128, 192, or 256 bits to encrypt and decrypt data in blocks of 128 bits.


A method of key exchange across a nonsecure environment (such as the Internet). The Diffie-Hellman algorithm negotiates a session key without sending the key itself across the network by allowing each party to pick a partial key independently and send part of that key to the other. Each side then calculates a common key value. This is a symmetrical method, and keys are typically used only for a short time, discarded, and regenerated.


Elliptic Curve Diffie-Hellman. A variant of the Diffie-Hellman key exchange algorithm that uses cryptography based on the algebraic structure of elliptic curves over finite fields. ECDH allows two parties, each having an elliptic curve public-private key pair, to establish a shared secret over an insecure channel. The shared secret can be used either as a key or to derive another key for encrypting subsequent communications using a symmetric key cipher.


Elliptic Curve Digital Signature Algorithm. A variant of the Digital Signature Algorithm (DSA) that uses cryptography based on the algebraic structure of elliptic curves over finite fields. The bit size of the elliptic curve determines the difficulty of decrypting the key. The public key needed for ECDSA is about twice the size of the security strength in bits.


Defined as Keyed-Hashing for Message Authentication in RFC 2104, HMAC combines hashing algorithms with cryptographic keys for message authentication.

3DES (3des-cbc)

Encryption standard based on the original Data Encryption Standard (DES) from the 1970s that used a 56-bit key and was cracked in 1997. The more secure 3DES is DES enhanced with three multiple stages and effective key lengths of about 112 bits. For Junos OS in FIPS mode of operation, 3DES is implemented with cipher block chaining (CBC).