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Cryptographic Algorithms

The Cosmian server supports a large, and growing, list of cryptographic algorithms. This page lists the supported algorithms, their details and their reference in various standards. FIPS compliant algorithms are also listed with the corresponding NIST standard.

Keys and certificates for all the listed algorithms can be generated, imported, exported, wrapped, unwrapped… using the Cosmian KMS server API or command line interface tool

Should you require a specific algorithm or standard to be supported, please directly open a ticket or pull request on the Github repository.

Key-wrapping schemes

The Cosmian server supports key-wrapping via the Import(unwrapping) and Export (wrapping) kmip operations. The (un)wrapping key identifier may be that of a key or a certificate. In the latter case, the public key (or the associated private key for unwrapping, if any) will be retrieved and used.

The supported key-wrapping algorithms are:

Algorithm Wrap Key Type FIPS mode Description
AES-KWP Symmetric key wrapping NIST SP 800-38F Symmetric key-wrapping with padding as defined in RFC5649.
CKM_RSA_PKCS RSA PKCS#1 v1.5 Not anymore RSA WITH PKCS#1 v1.5 padding - removed by NIST approved algorithms for key wrapping in FIPS 140-3
CKM_RSA_PKCS_OAEP RSA key wrapping NIST 800-56B rev. 2 RSA OAEP with NIST approved hashing functions for RSA key size 2048, 3072 or 4096 bits.
CKM_RSA_AES_KEY_WRAP RSA-AES hybrid key wrapping NIST SP 800-38F RSA OAEP with NIST approved hashing functions and AES-KWP for RSA key size 2048, 3072 or 4096 bits.
Salsa Sealed Box X25519, Ed25519 and Salsa20 Poly1305 No ECIES compatible with libsodium Sealed Boxes.
ECIES P-192, P-224, P-256, P-384, P-521 No ECIES with a NIST curve and using SHAKE 128 and AES 128 GCM (P-192, P-224, P-256) AES 256 GCM otherwise.

Any encryption scheme below can be used for key-wrapping as well.

Encryption schemes

Encryption is supported via the Encrypt and Decrypt kmip operations. For bulk operations (i.e. encrypting/decrypting multiple data with the same key), please refer to KMIP Messages that allow combining multiple operations in a single request.

Encryption can be performed using a key or a certificate. Decryption can be performed using a key.

The supported encryption algorithms are:

Algorithm Encryption Key Type FIPS mode Description
Covercrypt Covercrypt No A fast post-quantum attribute based scheme: Covercrypt.
AES GCM Symmetric authenticated encryption with additional data NIST FIPS 197 The NIST standardized symmetric encryption in FIPS 197.
AES XTS Symmetric, not authenticated NIST SP 800-38E Used in disk encryption. Requires 2 keys (e.g. a double-sized key)
AES GCM-SIV Symmetric, authenticated, synthetic IV No Used for deterministic encryption and encryption of very large data sets.
ChaCha20-Poly1305 Symmetric authenticated encryption with additional data No A popular symmetric encryption algorithm standardized in RFC-8439
CKM_RSA_PKCS RSA PKCS#1 v1.5 Not anymore RSA WITH PKCS#1 v1.5 padding - removed by NIST approved algorithms for encryption in FIPS 140-3
CKM_RSA_PKCS_OAEP RSA encryption with OAEP padding NIST 800-56B rev. 2 RSA OAEP with NIST approved hashing functions for RSA key size 2048, 3072 or 4096 bits.
Salsa Sealed Box X25519, Ed25519 and Salsa20 Poly1305 No ECIES compatible with libsodium Sealed Boxes.
ECIES P-192, P-224, P-256, P-384, P-521 No ECIES with a NIST curve and using SHAKE 128 and AES-128-GCM.

Algorithms Details

Covercrypt

Covercrypt is a new post-quantum cryptographic algorithm, being standardized at ETSI that allows creating ciphertexts for a set of attributes and issuing user keys with access policies over these attributes. User keys are traceable with a unique fingerprint.

AES GCM

AES is described in NIST FIPS 197. In Cosmian KMS it is used as a data encryption mechanism (DEM) with the Galois Counter Mode of operation (GCM) with a 96 bits nonce, a 128 bits tag with and key sizes of 128 or 256 bits.

ChaCha20-Poly1305

ChaCha20-Poly1305 is a symmetric authenticated encryption algorithm that is described in RFC-8439. The algorithm is not standardized by NIST but is a popular secure alternative to AES-GCM and is used in the same way, in particular by Google.

AES-KWP

Allows to symmetrically wrap keys using RFC5649 which is also standardized as PKCS#11 CKM_AES_KEY_WRAP_PAD and described in NIST SP 800-38F.

CKM_RSA_PKCS

A.k.a PKCS #1 v1.5 RSA as specified in PKCS#11 v2.40.

The algorithm is not recommended by NIST for encryption or key wrapping in FIPS 140-3. It is still supported for signature operations.

The maximum plaintext length is k-11 where k is the length in octets of the RSA modulus The output length is the same as the modulus length.

CKM_RSA_PKCS_OAEP

A.k.a PKCS #1 RSA OAEP as specified in PKCS#11 v2.40. This scheme is part of the NIST 800-56B rev. 2 recommendation available at section 7.2.2.

The maximum plaintext length is k-2-2*hLen where

  • k is the length in octets of the RSA modulus
  • hLen is the length in octets of the hash function output

The output length is the same as the modulus length.

The default hash function is SHA-256 but any NIST approved hash functions can be used for the OAEP scheme as listed in

Set the corresponding name of the hash function in the Cryptographic Parameters when performing a KMIP operation.

To request this algorithm using the KMIP Encrypt/Decrypt operation, or key-wrapping as part of the Import/Export operations, specify the id/tags of an RSA key and set the Cryptographic Algorithm to RSA.

CKM_RSA_AES_KEY_WRAP

A PKCS#11 key wrapping mechanism that is supported by most HSMs.

The scheme asymmetrically wrap keys as described here and allows wrapping keys of any size using using a hybrid RSA/AES scheme.

Since old similar wrapping methods based on RSA used naive RSA encryption and could present some flaws, it aims at a generally more secure method to wrap keys:

  • Receive data of the form c|wk where | is the concatenation operator. Distinguish c and wk, respectively the encrypted kek and the wrapped key. First decrypt the key-encryption-key kek using RSA-OAEP, then proceed to unwrap the key by decrypting m = dec(wk, kek) using AES-KWP as specified in RFC5649.

The algorithm can be used with any NIST approved hash function described above; set the corresponding value in the Cryptographic Parameters when performing a KMIP operation.

To request this algorithm using key-wrapping as part of the Import/Export operations, specify the id of an RSA key as the key wrapping key and set the Cryptographic Algorithm to AES.

This algorithm is compatible with the one used in Google KMS.

RSA OAEP AES 128 GCM

CKM_RSA_AES_KEY_WRAP can only be used for key wrapping and not for encryption. This scheme adds authentication by using AES 128 in Galois Counter Mode (GCM). Combined with RSA OAEP to encapsulate the AES key, this scheme is compatible with NIST SP 800-38F.

To request this algorithm using the KMIP Encrypt/Decrypt operation, specify the id/tags of an RSA key and set the Cryptographic Algorithm to AES.

Salsa sealed box

An ECIES scheme that uses X25519 and XSalsa20-Poly1305 and is compatible with libsodium Sealed Boxes.

An Ed25519 key can be used; it will be automatically converted to X25519 first.

Ecies with NIST Curves

Although there is no specific FIPS standard for hybrid encryption, the ECIES encryption scheme is based on FIPS compliant cryptographic primitives only and uses the same algorithm as the Salsa Sealed Boxes. It supports the entire family of NIST P curves, with the exception of P-192 in FIPS mode, and uses AES-128-GCM and SHAKE128 for curves with security strength s \leq 128 bits:

  • P-192
  • P-224
  • P-256

and AES-256-GCM and SHAKE256 for curves with security strength s > 128 bits:

  • P-384
  • P-512

Signature

Signature is only supported via the Certify operation, which is used to create a certificate either by signing a certificate request, or building it from an existing public key.

Algorithm Signature Key Type FIPS mode Description
ECDSA P-192, P-224, P-256, P-384, P384, P-521, X25519, X448 Restricted to curves P-224, P-256, P-384 and P-521. See FIPS-186.5 and NIST.SP.800-186 - Section 3.1.2 table 2.
EdDSA Ed25519, Ed448 Yes See FIPS-186.5.
  • ECDSA performs digital signatures on elliptic curves P-192, P-224, P-256, P-384, P-512, X25519 and X448.
  • EdDSA performs digital signatures on Edwards curves Ed25519 and Ed448.

Password-based key derivation

The randomness of cryptographic keys is essential for the security of cryptographic applications. Sometimes, passwords may be the only input required from the users who are eligible to access the data. Due to the low entropy and possibly poor randomness of those passwords, they are not suitable to be used directly as cryptographic keys. The KMS addresses this problem by providing methods to derive a password into a secure cryptographic key.

In normal mode, passwords are derived using Argon2 hash algorithm with a random 128-bit salt. Argon2 has the property of being computationally intensive making it significantly harder to crack by brute force only.

In FIPS mode, passwords are derived using FIPS compliant PBKDF2_HMAC with SHA512 and recommended 210,000 iterations by OWASP which follows FIPS recommendations as well. An additional random 128-bit salt is used.

References

  • NIST.FIPS.140-3, Implementation Guidance for FIPS 140-3 and the Cryptographic Module Validation Program, August 1, 2023

    • General information and pointers to other NIST documents concerning the FIPS standard.

  • NIST.SP.800-186, Recommendations for Discrete Logarithm-based Cryptography: Elliptic Curve Domain Parameters, February 2023

    • Recommended curves for specific usage (ECDH, ECDSA, EdDSA, …) and associated security strength. Describes each curves parameters in details.

  • NIST.SP.800-38F, Recommendation for Block Cipher Modes of Operation: Methods for Key Wrapping, December 2012

    • Description of symmetric key wrapping using AES-KW and AES-KWP. Approving RFC 5649.

  • NIST.FIPS.800-132, Recommendation for Password-Based Key Derivation, December 2010

    • Description of low-entropy data derivation into secure master key.

  • NIST.SP.800-56Cr2, Recommendation for Key-Derivation Methods in Key-Establishment Schemes, August 2020

    • Description of high-entropy data derivation into secure master key.

  • NIST.SP.800-131Ar2, Transitioning the Use of Cryptographic Algorithms and Key Lengths, March 2019

    • Key length specification for different domain parameters, algorithms and cryptographic schemes.

  • NIST.SP.800-56Ar3, Recommendation for Pair-Wise Key-Establishment Schemes Using Discrete Logarithm Cryptography, April 2018

    • General information on discrete logarithm parameters.

  • NIST.SP.800-56Br2, Recommendation for Pair-Wise Key Establishment Using Integer Factorization Cryptography, March 2019

    • Information regarding RSA primitive specifications: key length, encryption, decryption and padding to use.

  • NIST.FIPS.180-4, Secure Hash Standard (SHS), August 2015

    • Specification regarding SHA family of hash functions.

  • NIST.FIPS.202, SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions, August 2015

    • Specification for SHA3.

  • NIST.FIPS.186-5, Digital Signature Standard (DSS), February 3, 2023

    • Information on ECDSA, EdDSA and key generation.

  • NIST.FIPS.800-135r1, Recommendation for Existing Application-Specific Key Derivation Functions, December 2011

  • OpenSSL FIPS 140-2 Security Policy, 26 January 2023

    • OpenSSL official documentation

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