livecodingspace-app/public/lib/gundb/sea/decrypt.js

    var SEA = require('./root');
    var shim = require('./shim');
    var S = require('./settings');
    var aeskey = require('./aeskey');

    SEA.decrypt = SEA.decrypt || (async (data, pair, cb, opt) => { try {
      opt = opt || {};
      var key = (pair||opt).epriv || pair;
      if(!key){
        pair = await SEA.I(null, {what: data, how: 'decrypt', why: opt.why});
        key = pair.epriv || pair;
      }
      var json = S.parse(data);
      var buf, bufiv, bufct; try{
        buf = shim.Buffer.from(json.s, opt.encode || 'base64');
        bufiv = shim.Buffer.from(json.iv, opt.encode || 'base64');
        bufct = shim.Buffer.from(json.ct, opt.encode || 'base64');
        var ct = await aeskey(key, buf, opt).then((aes) => (/*shim.ossl ||*/ shim.subtle).decrypt({  // Keeping aesKey scope as private as possible...
          name: opt.name || 'AES-GCM', iv: new Uint8Array(bufiv), tagLength: 128
        }, aes, new Uint8Array(bufct)));
      }catch(e){
        if('utf8' === opt.encode){ throw "Could not decrypt" }
        if(SEA.opt.fallback){
          opt.encode = 'utf8';
          return await SEA.decrypt(data, pair, cb, opt);
        }
      }
      var r = S.parse(new shim.TextDecoder('utf8').decode(ct));
      if(cb){ try{ cb(r) }catch(e){console.log(e)} }
      return r;
    } catch(e) { 
      console.log(e);
      SEA.err = e;
      if(SEA.throw){ throw e }
      if(cb){ cb() }
      return;
    }});

    module.exports = SEA.decrypt;