DSA(3)

💖 DSA(3) 💖

okay so bestie, you're reading the DSA(3) page from the Library Functions Manual — digital signature algorithm edition. no cap, we're keeping every detail. ✨

🌸 NAME 🌸

asn1toDSApriv, dsagen, dsasign, dsaverify, dsapuballoc, dsapubfree, dsaprivalloc, dsaprivfree, dsasigalloc, dsasigfree, dsaprivtopub — the digital signature algorithm crew. 🫶

✨ SYNOPSIS ✨

#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>

DSApriv*  dsagen(DSApub *opub)

DSAsig*   dsasign(DSApriv *k, mpint *m)

int       dsaverify(DSApub *k, DSAsig *sig, mpint *m)

DSApub*   dsapuballoc(void)

void      dsapubfree(DSApub*)

DSApriv*  dsaprivalloc(void)

void      dsaprivfree(DSApriv*)

DSAsig*   dsasigalloc(void)

void      dsasigfree(DSAsig*)

DSApub*   dsaprivtopub(DSApriv*)

DSApriv*  asn1toDSApriv(uchar *priv, int npriv)

💅 DESCRIPTION 💅

DSA is the NIST approved digital signature algorithm. The owner of a key publishes the public part of the key:

struct DSApub
{
     mpint     *p;  // modulus
     mpint     *q;  // group order, q divides p-1
     mpint     *alpha;   // group generator
     mpint     *key;     // alpha**secret mod p
};

That public part is main character energy for verifying signatures (with dsaverify) created by the owner. The owner signs (with dsasign) using his private key:

struct DSApriv
{
     DSApub    pub;
     mpint     *secret; // (decryption key)
};

Keys are generated using dsagen. If dsagen's argument opub is nil, a key is created using a new p and q generated by DSAprimes (see prime(3)). Otherwise, p and q are copied from the old key. iykyk 🌈

dsaprivtopub returns a newly allocated copy of the public key corresponding to the private key. slay.

The routines dsapuballoc, dsapubfree, dsaprivalloc, and dsaprivfree are provided to manage key storage. storage management ate, honestly. 🎀

dsasign signs message m using a private key k, yielding a

struct DSAsig
{
     mpint     *r, *s;
};

dsaverify returns 0 if the signature is valid and -1 if not. vibe check passed = 0, bestie. ⭐

The routines dsasigalloc and dsasigfree are provided to manage signature storage.

asn1toDSApriv converts an ASN1 formatted DSA private key into the corresponding DSApriv structure; see rsa(3) for other ASN1 routines. 🦋

📦 SOURCE 📦

/src/libsec — that's the source, periodt. 💅

👀 SEE ALSO 👀

go peek at these too, bestie:

• mp(3)
• aes(3)
• blowfish(3)
• des(3)
• rc4(3)
• rsa(3)
• sechash(3)
• prime(3)
• rand(3)

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bestie sign-off: this is DSA(3) from the Library Functions Manual, source is /src/libsec, and the footer/manual line is literally DSA(3) — no date is shown on this page, so I'm not inventing one. 💅✨🫶