The Heart Sutra was not Historically seen as Authentic.

I was looking again at how Kazuaki Tanahashi presents the modern scholarship on the Heart Sutra and came across this quote:

"According to Fukui [Fumimasa], there has not been a single record or argument in Chinese history that suggests the Heart Sutra is an apocryphal text." (Tanahashi 2014: 77)

Fukui is responding to Jan Nattier's 1992 article which explains that the quoted section in the Heart Sutra (about half the text) is an extract from the Chinese Dajing translation produced by Kumārajīva et al (T223). He could not be more wrong. Here are the historical Chinese sources that contradict him.

1. Catalogue by Dàoān, 道安 in 374. Although this catalogue is itself lost, Sēngyòu reproduces much of it in his catalogue (T2145). Dàoān categorises the 摩訶般若波羅蜜神呪 (supposedly the Heart Sutra) as "unknown translator" and lists apart from authentic sutras.
2. 《出三藏記集》Chūsānzàng jìjí or Collection of Records about the Production of the Tripiṭaka (T2145), produced 515 CE by Sēngyòu (僧祐 445–518). Lists 摩訶般若波羅蜜神呪 as "unknown translator" and lists apart from authentic sutras.
3. 《大隋眾經目錄》 or Dà Suí Catalogue compiled in 594 by Fǎjīng also lists titles 《 摩訶般若波羅蜜神呪經》 and 《般若波羅蜜神呪經》 (T 55.123.b.22-3) under the heading of Mahāyāna texts "produced separately" (別生). As Tokuno notes, this category was invented by Fǎjīng to contain the digest sutras (抄經).
4. 《歷代三寳記》 Records of the Three Treasuries Throughout Successive Dynasties, compiled by Fèi Chángfáng (費長房 ) in 597 CE (T2034). Lists the 《般若波羅蜜神呪經》 with an annotation 或無經字 "perhaps not a sutra" (T 49.55.c.1).
5. 《內典文全集》 Complete collection of Buddhist scriptures (T2147) in 602 CE. Yàncóng was a skilled and systematic translator and an expert on Prajñāpāramitā. Yàncóng's catalogue again lists 《摩訶般若波羅蜜神呪經》 and 《般若波羅蜜神呪經》 (T 55.162.a.24-5) under the heading 大乘別生 or "Mahāyāna Produced Separately", i.e. digests of Mahāyāna sutras.
6. 般若波羅蜜多心經幽贊》 ( 2 卷)　Comprehensive Commentary on the Prañāpāramitā Heart Sutra 【唐 窺基撰】 [Tang Dynasty. Kuījī 窺基] T1710.  Refers to the Heart Sutra being produced separately (別出) by the sages, "rather than as preached by the Buddha" meaning he did not see it as an authentic sutra. 
7. 《般若波羅蜜多心經 贊》 ( 1 卷) Prañāpāramitā Heart Sutra Commentary.【唐 圓測撰】[Tang Dynasty. Woncheuk 圓測 (Pinyin: Yuáncè)] T1711.  "Since [this text] selects the essential outlines from all the Prajñāpāramitā-sūtras, it has only the main chapter, without introduction and conclusion, just as the Kuan-yin ching (Avalokiteśvara-sūtra) is not composed of three sections.

If indeed the 神呪 (vidyā? dhāraṇī?) texts are the Heart Sutra, then all of the catalogues are united in not considering them authentic sutras. And once the category of "digest text" (抄經) is identified, the 神呪 are always categorised with other digests. However, given that the Heart Sutra cannot be earlier than 404 CE, i.e. the date of the Dajing translation it quotes from (T223), then the 神呪 texts, which have continuity going back to 374 CE, are plainly not the Heart Sutra. 

The first evidence of the Heart Sutra is the Fangshan stele dated 661 CE with a text very like the Xīnjīng (T251). The Damingzhoujing (T250) doesn't make an appearance until 730. It plainly post-dates Xīnjīng and was produced as part of the legitimising myth for Xīnjīng. The fact is that, as good as he was, Xuanzang was never a popular translator. He never had the impact that Kumārajīva et al did. So adding a text attributed to Kumārajīva was a way to raise the status of the text. 

However, we know from internal evidence that the Chinese text is not a translation from Sanskrit at all. It is a digest text based on the Dajing. Therefore it is wrong to say that Xuanzang translated it. What is more, Kuījī and Woncheuk both knew this in the 7th Century.

Of course someone translated it into Sanskrit, which can only have been aimed at deceiving us into believing that the Xīnjīng was a translation. Where the Xīnjīng might be seen as a pious attempt to find the essence of Prajñāpāramitā, the Prajñāpāramitāhṛdaya (i.e. the Sanskrit translation of the Xīnjīng) can only have been made to deceive us about the origins of the Xīnjīng. Which it did. Ironically, is a cheap forgery full of Chinese idioms and nasty unidiomatic Sanskrit phrases. Had anyone been paying attention for the last 1300 years this would have been completely obvious.

Fukui is now deceased. So he cannot go on fulminating, although Japanese and Japanophiles continue to cite his flawed works and those by other parochial Japanese scholar-priests who do not like to face the truth.

See also my essay The True History of the Heart Sutra.