# FreeBSD Manual Pages

seccure(1) General Commands Manual seccure(1)NAMEseccure - SECCURE Elliptic Curve Crypto Utility for Reliable EncryptionSYNOPSISseccure-key[-ccurve][-Fpwfile][-d][-v][-q]seccure-encrypt[-mmaclen][-ccurve][-iinfile][-ooutfile][-v][-q]keyseccure-decrypt[-mmaclen][-ccurve][-iinfile][-ooutfile][-Fpw-file][-d][-v][-q]seccure-sign[-f][-b][-a][-ccurve][-ssigfile][-iinfile][-ooutfile][-Fpwfile][-d][-v][-q]seccure-verify[-f][-b][-a][-ccurve][-ssigfile][-iinfile][-ooutfile][-v][-q]key[sig]seccure-signcrypt[-csig_curve[-cenc_curve]][-iinfile][-oout-file][-Fpwfile][-d][-v][-q]keyseccure-veridec[-cenc_curve[-csig_curve]][-iinfile][-ooutfile][-Fpwfile][-d][-v][-q]keyseccure-dh[-ccurve][-v][-q]DESCRIPTIONTheseccuretoolset implements a selection of asymmetric algorithms based on elliptic curve cryptography (ECC). In particular it offers public key encryption / decryption, signature generation / verification and basic key establishment. ECC schemes offer a much better key size to security ratio than classi- cal cryptosystems (RSA, DSA). Keys are short enough to make direct specification of keys on the command line possible (sometimes this is more convenient than the management of PGP-like key rings).seccurebuilds on this feature and therefore is the tool of choice whenever lightweight but nevertheless strong asymmetric cryptography -- indepen- dent of key servers, revocation certificates, the Web of Trust or even configuration files -- is required.COMMANDSseccure-key: Prompt for a passphrase and calculate the corresponding public key.seccure-encrypt: Encrypt a message with public keykey.seccure-decrypt: Prompt for a passphrase and decrypt aseccure-en-crypted message.seccure-sign: Prompt for a passphrase and digitally sign a message.seccure-verify: Verify signaturesigwith public keykey.seccure-signcrypt: Sign a message first, encrypt it subsequently (in-b-aand-m0mode, respectively). This is basically a shortcut for two separateseccureinvocations.seccure-veridec: Counterpart to signcryption.seccure-dh: Perform a Diffie-Hellman key exchange.OPTIONS-ccurveUse elliptic curvecurve. Available are:secp112r1,secp128r1,secp160r1,secp192r1/nistp192,secp224r1/nistp224,secp256r1/nistp256,secp384r1/nistp384,secp521r1/nistp521,brainpoolp160r1,brainpoolp192r1,brainpoolp224r1,brain-poolp256r1,brainpoolp320r1,brainpoolp384r1, andbrain-poolp512r1. The curve name may be abbreviated by any non-ambigu- ous substring (for instance it is suggested to specifyp224for thesecp224r1/nistp224curve). The default curve isp160, which provides reasonable security for everyday use. (See alsoHOWTOCHOOSETHECURVE.) Note: If a public key is given on the command line, for all SECP and NIST curvesseccurecan determine the corresponding curve on its own. It is then unnecessary to specify the curve explicitly. Brainpool curves cannot be recognized automatically.-FpwfileDon't prompt for a passphrase; instead, take the first text line ofpwfile.-mmaclenSet the MAC length tomaclenbits. Only multiples of 8 in the range from 0 to 256 are allowed. The default MAC length is 80 bits, which provides a reasonable level of integrity protection for everyday use.-iinfileRead frominfileinstead of STDIN.-ooutfileWrite tooutfileinstead of STDOUT.-ssigfileForseccure-sign: Write signature tosigfileinstead of STDERR. Forseccure-verify: Read signature fromsigfileinstead of usingsig.-fFilter mode: Copy all data read from STDIN verbatim to STDOUT (eventually attaching or detaching a signature in-amode).-bBinary mode: Read/write signatures as binary strings. This leads to very compact signatures.-aAppend mode: Forseccure-sign: Append signature to the end of the document. This enforces-fmode. Forseccure-verify: Detach signature from the end of the docu- ment.-dDouble prompt mode: When reading a passphrase from the console: prompt twice and assure the phrases are the same.-vVerbose mode: Print some extra information.-qQuiet mode: Disable all unnecessary output.EXIT STATUSAll commands in theseccuresoftware suite exit with a status of zero if the desired operation could be completed successfully. Any error leads to a nonzero exit code.EXAMPLEGiven the passphrase 'seccure is secure', runseccure-keyto determine the corresponding public key (which is '2@DupCaCKykHBe-QH- pAP%d%B[' on curvep160). To encrypt the file 'document.msg' with that key runseccure-encrypt-idocument.msg-odocument.enc'2@DupCaCKykHBe-QH-pAP%d%B['The message can be recovered withseccure-decrypt-idocument.encTo sign the file runseccure-sign-idocument.msg-sdocument.sigand enter the passphrase. The signature is stored in 'document.sig' and can be verified withseccure-verify-idocument.msg-sdocument.sig'2@DupCaCKykHBe-QH-pAP%d%B['KEY ESTABLISHMENTseccure-dhperforms an interactive Diffie-Hellman key exchange. Two in- stances have to be run in parallel; the token generated by the first instance is the input for the second one and vice versa. The output consists of two shared keys: it is guaranteed that no attacker can ever find out (more precisely, distinguished from random) the established key as soon as the two parties can confirm that both have the same ver- ification key. The authentic comparision of the verification keys can, for example, be realized via signed messages or via telephone (using 'voice authentication').HOW TO CHOOSE THE CURVEThe number in the name of a curve measures its security level. Rule of thumb: the workload to 'break' a k-bit curve is 2^(k/2) approximately (example: it takes about 2^112 steps to breaksecp224r1). If the 80 bit security of the default curve doesn't seem sufficient, choosing a stronger curve (p192and upwards) may, of course, be considered. But the suggestion remains:p160offers reasonable security for everyday use.Warning:the curvesp112andp128do not satisfy demands for long- time security.ALGORITHMSseccureuses derivated versions of ECIES (Elliptic Curve Integrated En- cryption Scheme), ECDSA (Elliptic Curve Digital Signature Algorithm) and ECDH (Elliptic Curve Diffie-Hellman) as encryption, signature and key establishment scheme, respectively. For the symmetric parts (bulk encryption, hashing, key derivation, HMAC calculation)seccurebuilds on AES256 (in CTR mode), SHA256 and SHA512. To my best knowledge no part ofseccureis covered by patents. See the file PATENTS for an ex- plicit patent statement.AUTHORThis software (v0.5) was written by B. Poettering (seccure AT point-at- infinity.org) in 2006-2014. It is released under the terms of the GNU Lesser General Public License (LGPLv3). Find the latest version ofsec-cureon the project's homepage:http://point-at-infinity.org/seccure/. Manuals User seccure(1)

NAME | SYNOPSIS | DESCRIPTION | COMMANDS | OPTIONS | EXIT STATUS | EXAMPLE | KEY ESTABLISHMENT | HOW TO CHOOSE THE CURVE | ALGORITHMS | AUTHOR

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