Network Working Group A. Kato Internet-Draft NTT Software Corporation Intended status: Standards Track M. Kanda Expires: September 5, 2007 Nippon Telegraph and Telephone Corporation March 4, 2007 The Additional Modes of Operation for Camellia and Its Use With IPsec draft-kato-ipsec-camellia-modes-02 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 5, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Kato & Kanda Expires September 5, 2007 [Page 1] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 Abstract This document describes the use of the Camellia block cipher algorithm in Counter (CTR) mode and Counter with CBC-MAC (CCM) Mode , as an IPsec Encapsulating Security Payload (ESP) mechanism to provide confidentiality, data origin authentication, and connectionless integrity. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Camellia Cipher Algorithm . . . . . . . . . . . . . . . . 5 2.1. Key Size . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Weak Keys . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Block Size and Padding . . . . . . . . . . . . . . . . . . 5 2.4. Performance . . . . . . . . . . . . . . . . . . . . . . . 5 3. Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Counter . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Counter with CBC-MAC . . . . . . . . . . . . . . . . . . . 9 4. ESP Payload . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Counter . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.1. Counter Block Format . . . . . . . . . . . . . . . . . 12 4.1.2. Keying Material . . . . . . . . . . . . . . . . . . . 13 4.2. Counter with CBC-MAC . . . . . . . . . . . . . . . . . . . 13 4.2.1. Initialization Vector (IV) . . . . . . . . . . . . . . 13 4.2.2. Encrypted Payload . . . . . . . . . . . . . . . . . . 14 4.2.3. Authentication Data . . . . . . . . . . . . . . . . . 14 4.2.4. Nonce Format . . . . . . . . . . . . . . . . . . . . . 14 4.2.5. AAD Construction . . . . . . . . . . . . . . . . . . . 15 5. IKE Conventions . . . . . . . . . . . . . . . . . . . . . . . 17 5.1. Phase 1 Identifier . . . . . . . . . . . . . . . . . . . . 17 5.2. Phase 2 Identifier . . . . . . . . . . . . . . . . . . . . 17 5.3. Key Length Attribute . . . . . . . . . . . . . . . . . . . 17 6. Test Vectors . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.1. Normative . . . . . . . . . . . . . . . . . . . . . . . . 22 9.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 Intellectual Property and Copyright Statements . . . . . . . . . . 26 Kato & Kanda Expires September 5, 2007 [Page 2] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 1. Introduction This document describes the use of the Camellia block cipher algorithm in Counter mode and Counter with CBC-MAC (CCM) Mode , as an IPsec Encapsulating Security Payload (ESP) mechanism to provide confidentiality, data origin authentication, and connectionless integrity. Camellia is a symmetric cipher with a Feistel structure. Camellia was developed jointly by NTT and Mitsubishi Electric Corporation in 2000. It was designed to withstand all known cryptanalytic attacks, and it has been scrutinized by worldwide cryptographic experts. Camellia is suitable for implementation in software and hardware, offering encryption speed in software and hardware implementations that is comparable to Advanced Encryption Standard (AES) [18]. Camellia supports 128-bit block size and 128-, 192-, and 256-bit key lengths, i.e., the same interface specifications as the AES. Therefore, it is easy to implement Camellia based algorithms by replacing AES block of AES based algorithms to Camellia block. Camellia is adopted as IETF and several international standardization organizations. Camellia is already adopted as IPSec [17], TLS [15], S/MIME [12] and XML [14]. Camellia is adopted for the one of three ISO/IEC international standard cipher [21] as 128bit block cipher(Camellia AES and SEED). Camellia was selected as a recommended cryptographic primitive by the EU NESSIE (New European Schemes for Signatures, Integrity and Encryption) project [19] and was included in the list of cryptographic techniques for Japanese e-Government systems that was selected by the Japan CRYPTREC (Cryptography Research and Evaluation Committees) [20]. Since optimized source code is provided by several open source lisences [23], Camellia is also adopted by several open source projects. Camellia is already adopted by Openssl. Additional API for Network Security Services (NSS) and IPsec stack of Linux and Free BSD are prepared or working progress for release. The algorithm specification and object identifiers are described in [5]. The Camellia homepage [24] contains a wealth of information about Camellia, including detailed specification, security analysis, performance figures, reference implementation, optimized implementetion, test vectors, and intellectual property information. The remainder of this document specifies the additional modes of operation Camellia within the context of IPsec ESP. For further information on how the various pieces of ESP fit together to provide security services, please refer to [6] [7], and [3]. Kato & Kanda Expires September 5, 2007 [Page 3] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 1.1. Terminology The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" that appear in this document are to be interpreted as described in [1]. Kato & Kanda Expires September 5, 2007 [Page 4] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 2. The Camellia Cipher Algorithm All symmetric block cipher algorithms share common characteristics and variables, including mode, key size, weak keys, block size, and rounds. The following sections contain descriptions of the relevant characteristics of Camellia. The algorithm specification and object identifiers are described in [5]. 2.1. Key Size Camellia supports three key sizes: 128 bits, 192 bits, and 256 bits. The default key size is 128 bits, and all implementations MUST support this key size. Implementations MAY also support key sizes of 192 bits and 256 bits. Camellia uses a different number of rounds for each of the defined key sizes. When a 128-bit key is used, implementations MUST use 18 rounds. When a 192-bit key is used, implementations MUST use 24 rounds. When a 256-bit key is used, implementations MUST use 24 rounds. 2.2. Weak Keys At the time of writing this document there are no known weak keys for Camellia. 2.3. Block Size and Padding Camellia uses a block size of sixteen octets (128 bits). Padding is required by the algorithms to maintain a 16-octet (128- bit) block size. Padding MUST be added, as specified in [7], such that the data to be encrypted (which includes the ESP Pad Length and Next Header fields) has a length that is a multiple of 16 octets. Because of the algorithm specific padding requirement, no additional padding is required to ensure that the ciphertext terminates on a 4-octet boundary (i.e. maintaining a 16-octet block size guarantees that the ESP Pad Length and Next Header fields will be right aligned within a 4-octet word). Additional padding MAY be included, as specified in [7], as long as the 16-octet block size is maintained. 2.4. Performance Performance figures of Camellia are available at . NESSIE project has Kato & Kanda Expires September 5, 2007 [Page 5] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 reported performance of Optimized Implementations independently [19]. Kato & Kanda Expires September 5, 2007 [Page 6] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 3. Mode Camellia Counter mode (Camellia-CTR) and Camellia Counter with CBC- MAC (Camellia-CCM) are discussed in this specification. CCM is a generic authenticate-and-encrypt block cipher mode [4]. In this specification, CCM is used with the Camellia [5] block cipher. 3.1. Counter Camellia-CTR requires the encryptor to generate a unique per-packet value, and communicate this value to the decryptor. This specification calls this per-packet value an initialization vector (IV). The same IV and key combination MUST NOT be used more than once. The encryptor can generate the IV in any manner that ensures uniqueness. Common approaches to IV generation include incrementing a counter for each packet and linear feedback shift registers (LFSRs). This specification calls for the use of a nonce for additional protection against precomputation attacks. The nonce value need not be secret. However, the nonce MUST be unpredictable prior to the establishment of the IPsec security association that is making use of Camellia-CTR. Camellia-CTR has many properties that make it an attractive encryption algorithm for in high-speed networking. Camellia-CTR uses the Camellia block cipher to create a stream cipher. Data is encrypted and decrypted by XORing with the key stream produced by Camellia encrypting sequential counter block values. Camellia-CTR is easy to implement, and Camellia-CTR can be pipelined and parallelized. Camellia-CTR also supports key stream precomputation. Pipelining is possible because Camellia has multiple rounds (see section Section 2.). A hardware implementation (and some software implementations) can create a pipeline by unwinding the loop implied by this round structure. For example, after a 16-octet block has been input, one round later another 16-octet block can be input, and so on. In Camellia-CTR, these inputs are the sequential counter block values used to generate the key stream. Multiple independent Camellia encrypt implementations can also be used to improve performance. For example, one could use two Camellia encrypt implementations in parallel, to process a sequence of counter block values, doubling the effective throughput. The sender can precompute the key stream. Since the key stream does not depend on any data in the packet, the key stream can be Kato & Kanda Expires September 5, 2007 [Page 7] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 precomputed once the nonce and IV are assigned. This precomputation can reduce packet latency. The receiver cannot perform similar precomputation because the IV will not be known before the packet arrives. When used correctly, Camellia-CTR provides a high level of confidentiality. Unfortunately, Camellia-CTR is easy to use incorrectly. Being a stream cipher, any reuse of the per-packet value, called the IV, with the same nonce and key is catastrophic. An IV collision immediately leaks information about the plaintext in both packets. For this reason, it is inappropriate to use this mode of operation with static keys. Extraordinary measures would be needed to prevent reuse of an IV value with the static key across power cycles. To be safe, implementations MUST use fresh keys with Camellia-CTR. The Internet Key Exchange (IKE) [8] protocol can be used to establish fresh keys. IKE can also provide the nonce value. With Camellia-CTR, it is trivial to use a valid ciphertext to forge other (valid to the decryptor) ciphertexts. Thus, it is equally catastrophic to use Camellia-CTR without a companion authentication function. Implementations MUST use Camellia-CTR in conjunction with an authentication function, such as Camellia-CMAC-96 [22]. To encrypt a payload with Camellia-CTR, the encryptor partitions the plaintext, PT, into 128-bit blocks. The final block need not be 128 bits; it can be less. PT = PT[1] PT[2] ... PT[n] Each PT block is XORed with a block of the key stream to generate the ciphertext, CT. The Camellia encryption of each counter block results in 128 bits of key stream. The most significant 96 bits of the counter block are set to the nonce value, which is 32 bits, followed by the per-packet IV value, which is 64 bits. The least significant 32 bits of the counter block are initially set to one. This counter value is incremented by one to generate subsequent counter blocks, each resulting in another 128 bits of key stream. The encryption of n plaintext blocks can be summarized as: CTRBLK := NONCE || IV || ONE FOR i := 1 to n-1 DO CT[i] := PT[i] XOR Camellia(CTRBLK) CTRBLK := CTRBLK + 1 END CT[n] := PT[n] XOR TRUNC(Camellia(CTRBLK)) The Camellia() function performs Camellia encryption with the fresh key. Kato & Kanda Expires September 5, 2007 [Page 8] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 The TRUNC() function truncates the output of the Camellia encrypt operation to the same length as the final plaintext block, returning the most significant bits. Decryption is similar. The decryption of n ciphertext blocks can be summarized as: CTRBLK := NONCE || IV || ONE FOR i := 1 to n-1 DO PT[i] := CT[i] XOR Camellia(CTRBLK) CTRBLK := CTRBLK + 1 END PT[n] := CT[n] XOR TRUNC(Camellia(CTRBLK)) 3.2. Counter with CBC-MAC CCM is a generic authenticate-and-encrypt block cipher mode [4]. In this specification, CCM is used with the Camellia [5] block cipher. Camellia-CCM has two parameters: M M indicates the size of the integrity check value (ICV). CCM defines values of 4, 6, 8, 10, 12, 14, and 16 octets; However, to maintain alignment and provide adequate security, only the values that are a multiple of four and are at least eight are permitted. Implementations MUST support M values of 8 octets and 16 octets, and implementations MAY support an M value of 12 octets. L L indicates the size of the length field in octets. CCM defines values of L between 2 octets and 8 octets. This specification only supports L = 4. Implementations MUST support an L value of 4 octets, which accommodates a full Jumbogram [11]; however, the length includes all of the encrypted data, which also includes the ESP Padding, Pad Length, and Next Header fields. There are four inputs to CCM originator processing: key A single key is used to calculate the ICV using CBC-MAC and to perform payload encryption using counter mode. Camellia supports key sizes of 128 bits, 192 bits, and 256 bits. The default key size is 128 bits, and implementations MUST support this key size. Implementations MAY also support key sizes of 192 bits and 256 bits. Kato & Kanda Expires September 5, 2007 [Page 9] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 nonce The size of the nonce depends on the value selected for the parameter L. It is 15-L octets. Implementations MUST support a nonce of 11 octets. The construction of the nonce is described in Section 4.2.4. payload The payload of the ESP packet. The payload MUST NOT be longer than 4,294,967,295 octets, which is the maximum size of a Jumbogram [11]; however, the ESP Padding, Pad Length, and Next Header fields are also part of the payload. AAD CCM provides data integrity and data origin authentication for some data outside the payload. CCM does not allow additional authenticated data (AAD) to be longer than 18,446,744,073,709,551,615 octets. The ICV is computed from the ESP header, Payload, and ESP trailer fields, which is significantly smaller than the CCM-imposed limit. The construction of the AAD described in Section 4.2.5. Camellia-CCM requires the encryptor to generate a unique per-packet value and to communicate this value to the decryptor. This per- packet value is one of the component parts of the nonce, and it is referred to as the initialization vector (IV). The same IV and key combination MUST NOT be used more than once. The encryptor can generate the IV in any manner that ensures uniqueness. Common approaches to IV generation include incrementing a counter for each packet and linear feedback shift registers (LFSRs). Camellia-CCM employs counter mode for encryption. As with any stream cipher, reuse of the same IV value with the same key is catastrophic. An IV collision immediately leaks information about the plaintext in both packets. For this reason, it is inappropriate to use this CCM with statically configured keys. Extraordinary measures would be needed to prevent reuse of an IV value with the static key across power cycles. To be safe, implementations MUST use fresh keys with Camellia-CCM. The Internet Key Exchange (IKE) [2] protocol or IKEv2 [8] can be used to establish fresh keys. Kato & Kanda Expires September 5, 2007 [Page 10] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 4. ESP Payload The ESP payload is made up of the IV followed by raw cipher-text. Thus the payload field, as defined in [7], is broken down according to the following diagram: 4.1. Counter The Camellia counter block cipher block is 128 bits. Figure 1 shows the format of the counter block. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initialization Vector | | (8 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Encrypted Payload (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Authentication Data (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: ESP Payload Encrypted with Camellia-CTR The components of the counter block are as follows: Initialization Vector The Camellia-CTR IV field MUST be eight octets. The IV MUST be chosen by the encryptor in a manner that ensures that the same IV value is used only once for a given key. The encryptor can generate the IV in any manner that ensures uniqueness. Common approaches to IV generation include incrementing a counter for each packet and linear feedback shift registers (LFSRs). Including the IV in each packet ensures that the decryptor can generate the key stream needed for decryption, even when some packets are lost or reordered. Encrypted Payload The encrypted payload contains the ciphertext. Camellia-CTR mode does not require plaintext padding. However, ESP does require padding to 32-bit word-align the authentication data. The padding, Pad Length, and the Next Header MUST be concatenated with the plaintext before performing encryption, as described in [7]. Kato & Kanda Expires September 5, 2007 [Page 11] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 Authentication Data Since it is trivial to construct a forgery Camellia-CTR ciphertext from a valid Camellia-CTR ciphertext, Camellia-CTR implementations MUST employ a non-NULL ESP authentication method. Camellia-CMAC-96 [22] is a likely choice. 4.1.1. Counter Block Format The Camellia counter block cipher block is 128 bits. Figure 2 shows the format of the counter block. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initialization Vector (IV) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Block Counter | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Counter Block Format The components of the counter block are as follows: Nonce The Nonce field is 32 bits. As the name implies, the nonce is a single use value. That is, a fresh nonce value MUST be assigned for each security association. It MUST be assigned at the beginning of the security association. The nonce value need not be secret, but it MUST be unpredictable prior to the beginning of the security association. Initializetion Vector The IV field is 64 bits. As described in section 3.1, the IV MUST be chosen by the encryptor in a manner that ensures that the same IV value is used only once for a given key. Block Counter The block counter field is the least significant 32 bits of the counter block. The block counter begins with the value of one, and it is incremented to generate subsequent portions of the key stream. The block counter is a 32-bit big-endian integer value. Using the encryption process described in Section 3.1, this construction permits each packet to consist of up to: Kato & Kanda Expires September 5, 2007 [Page 12] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 (2^32)-1 blocks = 4,294,967,295 blocks = 68,719,476,720 octets This construction can produce enough key stream for each packet sufficient to handle any IPv6 jumbogram [11]. 4.1.2. Keying Material The minimum number of bits sent from the key exchange protocol to the ESP algorithm must be greater than or equal to the key size. The cipher's encryption and decryption key is taken from the first 128, 192, or 256 bits of the keying material. 4.2. Counter with CBC-MAC The ESP payload is composed of the IV followed by the ciphertext. The payload field, as defined in [7], is structured as shown in Figure 3. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initialization Vector | | (8 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Encrypted Payload (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Authentication Data (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: ESP Payload Encrypted with Camellia-CCM 4.2.1. Initialization Vector (IV) The Camellia-CCM IV field MUST be eight octets. The IV MUST be chosen by the encryptor in a manner that ensures that the same IV value is used only once for a given key. The encryptor can generate the IV in any manner that ensures uniqueness. Common approaches to IV generation include incrementing a counter for each packet and linear feedback shift registers (LFSRs). Including the IV in each packet ensures that the decryptor can generate the key stream needed for decryption, even when some Kato & Kanda Expires September 5, 2007 [Page 13] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 datagrams are lost or reordered. 4.2.2. Encrypted Payload The encrypted payload contains the ciphertext. Camellia-CCM mode does not require plaintext padding. However, ESP does require padding to 32-bit word-align the authentication data. The Padding, Pad Length, and Next Header fields MUST be concatenated with the plaintext before performing encryption, as described in [7]. When padding is required, it MUST be generated and checked in accordance with the conventions specified in [7]. 4.2.3. Authentication Data Camellia-CCM provides an encrypted ICV. The ICV provided by CCM is carried in the Authentication Data fields without further encryption. Implementations MUST support ICV sizes of 8 octets and 16 octets. Implementations MAY also support ICV 12 octets. 4.2.4. Nonce Format Each packet conveys the IV that is necessary to construct the sequence of counter blocks used by counter mode to generate the key stream. The Camellia counter block is 16 octets. One octet is used for the CCM Flags, and 4 octets are used for the block counter, as specified by the CCM L parameter. The remaining octets are the nonce. These octets occupy the second through the twelfth octets in the counter block. Figure 4 shows the format of the nonce. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Salt | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initialization Vector | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Nonce Format of CCM The components of the nonce are as follows: Salt The salt field is 24 bits. As the name implies, it contains an unpredictable value. It MUST be assigned at the beginning of the security association. The salt value need not be secret, but it Kato & Kanda Expires September 5, 2007 [Page 14] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 MUST NOT be predictable prior to the beginning of the security association. Initialization Vector The IV field is 64 bits. As described in Section 3.1, the IV MUST be chosen by the encryptor in a manner that ensures that the same IV value is used only once for a given key. This construction permits each packet to consist of up to: 2^32 blocks = 4,294,967,296 blocks = 68,719,476,736 octets This construction provides more key stream for each packet than is needed to handle any IPv6 Jumbogram [11]. 4.2.5. AAD Construction The data integrity and data origin authentication for the Security Parameters Index (SPI) and (Extended) Sequence Number fields is provided without encrypting them. Two formats are defined: one for 32-bit sequence numbers and one for 64-bit extended sequence numbers. The format with 32-bit sequence numbers is shown in Figure 5, and the format with 64-bit extended sequence numbers is shown in Figure 6. Sequence Numbers are conveyed canonical network byte order. Extended Sequence Numbers are conveyed canonical network byte order, placing the high-order 32 bits first and the low-order 32 bits second. Canonical network byte order is fully described in RFC 791, Appendix B. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SPI | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 32-bit Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: AAD Format with 32-bit Sequence Number Kato & Kanda Expires September 5, 2007 [Page 15] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SPI | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 64-bit Extended Sequence Number | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: AAD Format with 64-bit Sequence Number Kato & Kanda Expires September 5, 2007 [Page 16] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 5. IKE Conventions Camellia was designed to follow the same API as the AES cipher. Therefore, this section defines only Phase 1 Identifier and Phase 2 Identifier. Any other consideration related to interaction with IKE is the same as that of the AES cipher. Details can be found in IKE Conventions section of [13] and [16]. 5.1. Phase 1 Identifier This document does not specify the conventions for using Camellia-CTR and Camellia-CCM for IKE Phase 1 negotiations. For Camellia-CTR and Camellia-CCM to be used in this manner, a separate specification is needed, and an Encryption Algorithm Identifier needs to be assigned. 5.2. Phase 2 Identifier For IKE Phase 2 negotiations, IANA has assigned three ESP Transform Identifiers for Camellia-CTR and Camellia-CCM. for Camellia-CTR with and explict IV; for Camellia-CCM with an 8-octet ICV; for Camellia-CCM with a 12-octet ICV; and for Camellia-CCM with a 16-octet ICV. 5.3. Key Length Attribute Since the Camellia supports three key lengths, the Key Length attribute MUST be specified in the IKE Phase 2 exchange [10]. The Key Length attribute MUST have a value of 128, 192, or 256. Kato & Kanda Expires September 5, 2007 [Page 17] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 6. Test Vectors Kato & Kanda Expires September 5, 2007 [Page 18] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 7. Security Considerations Camellia-CTR and Camellia-CCM employs counter (CTR) mode for confidentiality. If a counter value is ever used for more that one packet with the same key, then the same key stream will be used to encrypt both packets, and the confidentiality guarantees are voided. What happens if the encryptor XORs the same key stream with two different packet plaintexts? Suppose two packets are defined by two plaintext byte sequences P1, P2, P3 and Q1, Q2, Q3, then both are encrypted with key stream K1, K2, K3. The two corresponding ciphertexts are: (P1 XOR K1), (P2 XOR K2), (P3 XOR K3) (Q1 XOR K1), (Q2 XOR K2), (Q3 XOR K3) If both of these two ciphertext streams are exposed to an attacker, then a catastrophic failure of confidentiality results, because: (P1 XOR K1) XOR (Q1 XOR K1) = P1 XOR Q1 (P2 XOR K2) XOR (Q2 XOR K2) = P2 XOR Q2 (P3 XOR K3) XOR (Q3 XOR K3) = P3 XOR Q3 Once the attacker obtains the two plaintexts XORed together, it is relatively straightforward to separate them. Thus, using any stream cipher, including Camellia-CTR, to encrypt two plaintexts under the same key stream leaks the plaintext. Therefore, Camellia-CTR and Camellia-CCM should not be used with statically configured keys. Extraordinary measures would be needed to prevent the reuse of a counter block value with the static key across power cycles. To be safe, implementations MUST use fresh keys with Camellia-CTR and Camellia-CCM. The IKE [2] and IKEv2 [8] protocol can be used to establish fresh keys. When IKE is used to establish fresh keys between two peer entities, separate keys are established for the two traffic flows. If a different mechanism is used to establish fresh keys, one that establishes only a single key to encrypt packets, then there is a high probability that the peers will select the same IV values for some packets. Thus, to avoid counter block collisions, ESP implementations that permit use of the same key for encrypting and decrypting packets with the same peer MUST ensure that the two peers assign different salt values to the security association (SA). Regardless of the mode used, Camellia with a 128-bit key is Kato & Kanda Expires September 5, 2007 [Page 19] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 vulnerable to the birthday attack after 2^64 blocks are encrypted with a single key. Since ESP with Extended Sequence Numbers allows for up to 2^64 packets in a single SA, there is real potential for more than 2^64 blocks to be encrypted with one key. Implementations SHOULD generate a fresh key before 2^64 blocks are encrypted with the same key. Note that ESP with 32-bit Sequence Numbers will not exceed 2^64 blocks even if all of the packets are maximum-length Jumbograms. Kato & Kanda Expires September 5, 2007 [Page 20] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 8. IANA Considerations IANA has assigned three ESP transform numbers for use with Camellia- CTR and Camellia-CCM: for Camellia-CTR with and explict IV; for Camellia-CCM with an 8-octet ICV; for Camellia-CCM with a 12-octet ICV; and for Camellia-CCM with a 16-octet ICV. Kato & Kanda Expires September 5, 2007 [Page 21] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 9. References 9.1. Normative [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. [3] Thayer, R., Doraswamy, N., and R. Glenn, "IP Security Document Roadmap", RFC 2411, November 1998. [4] Whiting, D., Housley, R., and N. Ferguson, "Counter with CBC- MAC (CCM)", RFC 3610, September 2003. [5] Matsui, M., Nakajima, J., and S. Moriai, "A Description of the Camellia Encryption Algorithm", RFC 3713, April 2004. [6] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [7] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [8] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [9] Dworkin, M., "Recommendation for Block Cipher Modes of Operation - Methods and Techniques", NIST Special Publication 800-38A, November 2001, . 9.2. Informative [10] Piper, D., "The Internet IP Security Domain of Interpretation for ISAKMP", RFC 2407, November 1998. [11] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms", RFC 2675, August 1999. [12] Moriai, S. and A. Kato, "Use of the Camellia Encryption Algorithm in Cryptographic Message Syntax (CMS)", RFC 3657, January 2004. [13] Housley, R., "Using Advanced Encryption Standard (AES) Counter Mode With IPsec Encapsulating Security Payload (ESP)", RFC 3686, January 2004. Kato & Kanda Expires September 5, 2007 [Page 22] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 [14] Eastlake, D., "Additional XML Security Uniform Resource Identifiers (URIs)", RFC 4051, April 2005. [15] Moriai, S., Kato, A., and M. Kanda, "Addition of Camellia Cipher Suites to Transport Layer Security (TLS)", RFC 4132, July 2005. [16] Housley, R., "Using Advanced Encryption Standard (AES) CCM Mode with IPsec Encapsulating Security Payload (ESP)", RFC 4309, December 2005. [17] Kato, A., Moriai, S., and M. Kanda, "The Camellia Cipher Algorithm and Its Use With IPsec", RFC 4312, December 2005. [18] National Institute of Standards and Technology, "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001, . [19] "The NESSIE project (New European Schemes for Signatures, Integrity and Encryption)", . [20] Information-technology Promotion Agency (IPA), "Cryptography Research and Evaluation Committees", . [21] International Organization for Standardization, "Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers", ISO/IEC 18033-3, July 2005. [22] Kato, A., Kanda, M., and T. Iwata, "The Camellia-CMAC-96 and Camellia-CMAC-PRF-128 Algorithms and Its Use with IPsec", draft-kato-ipsec-camellia-cmac96and128-00 (work in progress), February 2007. Kato & Kanda Expires September 5, 2007 [Page 23] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 URIs [23] [24] Kato & Kanda Expires September 5, 2007 [Page 24] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 Authors' Addresses Akihiro Kato NTT Software Corporation Phone: +81-45-212-7094 Fax: +81-45-212-7506 Email: akato@po.ntts.co.jp Masayuki Kanda Nippon Telegraph and Telephone Corporation Phone: +81-46-859-2437 Fax: +81-46-859-3365 Email: kanda@isl.ntt.co.jp Kato & Kanda Expires September 5, 2007 [Page 25] Internet-Draft The Additional Modes of Camellia in IPsec March 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Kato & Kanda Expires September 5, 2007 [Page 26]